Little Giant Ladder Systems, LLC v. Tricam Industries, Inc.

NOTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
LITTLE GIANT LADDER SYSTEMS, LLC,
Plaintiff-Appellant
v.
TRICAM INDUSTRIES, INC.,
Defendant-Appellee
______________________
2024-2115
______________________
Appeal from the United States District Court for the
District of Minnesota in No. 0:20-cv-02497-KMM-ECW,
Judge Katherine Marie Menendez.
______________________
Decided: February 5, 2026
______________________
MARK A. MILLER, Dorsey & Whitney LLP, Salt Lake
City, UT, argued for plaintiff-appellant. Also represented
by BRETT L. FOSTER, ELLIOT HALES; SHANNON L.
BJORKLUND, Minneapolis, MN.
ERIC HUGH CHADWICK, DeWitt LLP, Minneapolis, MN,
argued for defendant-appellee. Also represented by
ZACHARY PAUL ARMSTRONG.
______________________
Case: 24-2115 Document: 55 Page: 1 Filed: 02/05/2026

-- 1 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
2
Before REYNA and CHEN, Circuit Judges, and FREEMAN,
District Judge.1
CHEN, Circuit Judge.
Little Giant Ladder Systems, LLC (Little Giant) ap-
peals a decision of the United States District Court for the
District of Minnesota granting summary judgment of non-
infringement of U.S. Patent No. 10,767,416 (’416 patent) in
favor of Tricam Industries, Inc. (Tricam). See Little Giant
Ladder Sys., LLC v. Tricam Indus., Inc., No. 20-CV-2497
(KMM/ECW), 2024 WL 1332027 (D. Minn. Mar. 28, 2024),
vacated in part (Apr. 12, 2024), modified and superseded by
No. 20-CV-2497 (KMM/ECW), 2024 WL 3014862 (D. Minn.
June 14, 2024) (D. Minn. June 14, 2024) (Summary Judg-
ment Order).2 The district court determined that “the ac-
cused products do not literally infringe the ‘cavity’
limitation and prosecution history estoppel bars Little Gi-
ant from relying on the doctrine of equivalents.” Id. at *1.
For the reasons below, we affirm.
BACKGROUND
Little Giant and Tricam are competitors in the ladder
industry. Summary Judgment Order, 2024 WL 1332027,
at *1. Little Giant alleged that Tricam’s ladders use a lock-
ing mechanism (called Speed Lock) that infringes the ’416
patent. Id. at *2–3.
The ’416 patent discloses a multi-position ladder with
two sets of rails and a locking mechanism. ’416 patent, Ab-
stract. The inventors recognized that operating a prior art
ladder “can result in the pinching of one[’]s fingers or
1 Honorable Beth Labson Freeman, District Judge,
United States District Court for the Northern District of
California, sitting by designation.
2 The June 14, 2024 Order did not modify issues pre-
sented in this opinion.
Case: 24-2115 Document: 55 Page: 2 Filed: 02/05/2026

-- 2 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
3
hands” and “can be awkward and difficult for some people
to perform.” Id., col. 1 ll. 59–60; id., col. 2 ll. 5–6. Accord-
ingly, the ’416 patent is directed to improved ladders with
“enhanced ease of use, stability[,] and safety.” Id., col. 2 ll.
17–21. The ‘416 patent has one independent claim, which
recites:
1. A ladder comprising:
a first assembly having a first pair of rails
including a first rail and a second rail, and
a second pair of rails including a third rail
and a fourth rail, the first pair of rails being
slidably coupled with the second pair rails;
and
a first locking mechanism comprising:
a first bracket coupled with the
first rail,
a first component rotatable about a
defined axis,
a first engagement pin coupled
with the first component, wherein
the first locking mechanism is con-
figured so that the first component
is rotatable from a first rotational
position to a second rotational posi-
tion;
wherein, when the first component
is in the first rotational position, a
substantial amount of the first
bracket is disposed within a cavity
defined by the first component and
the first engagement pin extends
through a pair of aligned openings
including a first opening formed in
Case: 24-2115 Document: 55 Page: 3 Filed: 02/05/2026

-- 3 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
4
the first rail and a second opening
formed in third rail, and
wherein, when the first component
is in the second rotational position,
the first engagement pin is with-
drawn from at least one of the first
opening and the second opening,
at least one retaining mechanism
configured to maintain the first
component in the first rotational
position until application of a first
force is applied to the first compo-
nent to displace it towards the sec-
ond rotational position, and
wherein the at least one retaining
mechanism is further configured to
maintain the first component in the
second rotational position until ap-
plication of a second force is applied
to the first component.
Id. at claim 1 (emphasis added).3
The disputed claim term “cavity” is recited in the con-
text of a locking mechanism. The locking mechanism ena-
bles height adjustment of the ladder by engaging or
releasing the inner rails from the outer rails of the ladder.
Id., col. 4 ll. 47–67 (descriptions of a ladder). The locking
mechanism includes a bracket (“first bracket”) such as
bracket 153 and a lever (“first component”) such as lever
152. See id., col. 2 ll. 31–32, 46–49; see also id., FIG. 14.
The lever is configured to pivot between two states: a
locked state (“first rotational position”) shown in Figure
3 The emphasized limitation is referred to as the cav-
ity limitation.
Case: 24-2115 Document: 55 Page: 4 Filed: 02/05/2026

-- 4 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
5
13A and an unlocked state (“second rotational position”)
shown in Figure 13B.
See ’416 patent, col. 7 ll. 26–31; id., FIGs. 13A–B.
The district court construed “cavity” to mean “a hol-
lowed-out space (not passing all the way through).” Little
Giant Ladder Sys., LLC v. Tricam Indus., Inc., No. 20-CV-
2497 (KMM/ECW), 2022 WL 2287048, at *8–10 (D. Minn.
June 24, 2022) (Claim Construction Order). The court
noted that the parties “essentially agreed[]” upon the
meaning of cavity and “both parties suggest inclusion of
[not passing all the way through].” Id. at *9. The court
explained that unlike a tunnel that passes all the way
through, the “cavity” does not pass all the way through the
“first component” (e.g., lever 152 from Figure 13A because
the cavity is bounded at one end by the rounded, upper por-
tion of the lever 152). Id. The court also construed “sub-
stantial amount” of the first bracket to mean “more than a
majority” of the first bracket and “disposed within” to mean
“placed inside of.” Id. at *4–8. Taken together, the cavity
limitation was construed as “more than a majority of the
first bracket is placed inside of a hollowed-out space (not
passing all the way through) defined by the first compo-
nent.” Id. at *10.
After claim construction, the parties exchanged their
expert reports and filed cross-motions for summary
Case: 24-2115 Document: 55 Page: 5 Filed: 02/05/2026

-- 5 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
6
judgment. Summary Judgment Order, 2024 WL 1332027,
at *1. Before addressing the summary judgment motions,
the court granted Tricam’s motion to exclude the testimony
of Little Giant’s expert, Mr. Smith, concerning infringe-
ment of the cavity limitation for failing to apply the court’s
construction. Id. at *22. The court rejected Mr. Smith’s
incorrect understanding that hollowed-out spaces un-
bounded on both ends (e.g., a tunnel or a taco shell) can be
the claimed cavity. Id. at *14–16.
The district court then granted Tricam’s motion for
summary judgment of noninfringement. Id. at *22. It did
so as to literal infringement because Little Giant’s sole ba-
sis for literal infringement of the “cavity” limitation rested
on Mr. Smith’s excluded opinion. Id. at *17. The court ex-
plained that the space in Tricam’s Speed Lock handle that
Little Giant asserted as the cavity cannot satisfy the
claimed cavity as properly construed, because that space is
akin to a tunnel that passes all the way through. Id. at
*16–17. As to infringement under the doctrine of equiva-
lents, the court applied amendment-based estoppel, finding
that Little Giant surrendered claim scope that encom-
passes non-cavity structures concealing the majority of the
bracket. Id. at *20.
Little Giant timely appealed. We have jurisdiction un-
der 28 U.S.C. § 1295(a)(1).
DISCUSSION
Little Giant appeals (1) the district court’s claim con-
struction of “cavity,”4 (2) its exclusion of Mr. Smith’s in-
fringement opinion, and (3) its summary judgment of
4 Little Giant is not appealing construction of any
other terms. See generally Appellant Br.; see also Appel-
lant Reply Br. 23 n.9.
Case: 24-2115 Document: 55 Page: 6 Filed: 02/05/2026

-- 6 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
7
noninfringement. See Appellant Br. 31–33. We address
each in turn.
I. Claim Construction
We review a district court’s claim construction de novo
and its underlying factual determinations for clear error.
See NexStep, Inc. v. Comcast Cable Commc'ns, LLC, 119
F.4th 1355, 1364 (Fed. Cir. 2024).
Little Giant urges us to construe the claimed “cavity”
to add a highly particularized meaning to the “does not
pass all the way through” portion of the district court’s con-
struction: “a hollowed-out space that doesn’t pass all the
way through in such a way that (i.e., in enough directions)
more than a majority of the bracket can be hidden or con-
cealed inside of that space.” Appellant Br. 33 (emphasis
omitted). Little Giant argues that the district court’s con-
struction “contradicts the plain meaning of ‘cavity’ and
stands in direct conflict with the intrinsic record.” Id. at
35. Alternatively, in its reply brief, Little Giant suggests
“cavity” should simply be “a hollowed-out space.” Appel-
lant Reply Br. 12.
We first address the inclusion of the adjectival phrase
“not passing all the way through.” Little Giant proposes to
remove this adjectival phrase, arguing that the plain and
ordinary meaning of “cavity” is broad. Appellant Reply Br.
2. We reject Little Giant’s invitation to rewrite the con-
struction, because the district court adopted the parties’
“essentially agreed-upon” construction of the claimed “cav-
ity” as a “hollowed-out space (not passing all the way
through).”5 Claim Construction Order, 2022 WL 2287048,
5 As part of its proposed construction of a larger
phrase, Little Giant argued that “cavity” should mean “a
hollowed out space (not passing all the way through).”
Claim Construction Order, 2022 WL 2287048, at *4.
Case: 24-2115 Document: 55 Page: 7 Filed: 02/05/2026

-- 7 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
8
at *8–10. Little Giant never argued below or in its opening
brief against the inclusion of the phrase “not passing all the
way through.” Instead, the opposite is true; it had consist-
ently maintained the inclusion of that phrase. J.A. 270,
1418–19, 2757; Appellant Br. 51–52. For this reason, we
find Little Giant’s reply brief position forfeited. See Wash
World Inc. v. Belanger Inc., 131 F.4th 1360, 1368–69 (Fed.
Cir. 2025); see TVIIM, LLC v. McAfee, Inc., 851 F.3d 1356,
1363 (Fed. Cir. 2017) (“[A] party may not introduce new
claim construction arguments on appeal or alter the scope
of the claim construction positions it took below.”) (citation
omitted). Accordingly, Little Giant is bound by the lan-
guage “not passing all the way through.”
Next, we address how to best read this adjectival
phrase.6 The origin of this phrase plainly comes from the
Notice of Allowance, where the patent examiner used this
exact phrase to articulate his conception of the claimed cav-
ity. J.A. 338. We understand that although Little Giant
argued for this phrase to be part of the construction of “cav-
ity,” it also below, as a gloss to that construction, explained
its particularized understanding of that phrase, which it
now asks this Court to formally incorporate into the claim
construction. See J.A. 268–70, 1417–19, 2741–42. Little
Giant explains that there was a disagreement about what
this language means. See Oral Arg. at 06:52 – 07:15; see
also J.A. 4988. In essence, Little Giant argues that this
Tricam’s proposed construction for “cavity” was essentially
the same: “a hollowed-out space in a mass that does not
pass all the way through.” Id. (emphasis added). Tricam
admits that inclusion or exclusion of “in a mass” does not
make a material difference. See Appellee Br. 14–15.
6 During oral argument, Little Giant agreed that
this is a fair characterization of the issue. Oral Arg. at
02:36 – 03:05 (available at https://www.cafc.uscourts.gov/
oral-arguments/24-2115_01082026.mp3).
Case: 24-2115 Document: 55 Page: 8 Filed: 02/05/2026

-- 8 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
9
adjectival phrase needs a directional elaboration (“in
enough directions”) and a concept of “hid[ing] or con-
ceal[ing]” the bracket. See Appellant Br. 40, 49. To explain
its position, Little Giant provides its diagrammatic depic-
tions (shown below) of lever 152 from Figures 13A and 13B
and also points to the examiner’s statement in the Notice
of Allowance. Id. at 50 (citing J.A. 338).
Appellant Br. 27 (Little Giant’s diagrammatic depictions).
We disagree that the Notice of Allowance supports Lit-
tle Giant’s proposed understanding of “not passing all the
way through.” There, the examiner interpreted the
claimed “cavity” as “a hollowed out space in a mass such as
a cavity in a tooth, where the hollowed space doesn’t pass
all the way through [as shown by the drawings in the in-
stant invention] such that the first component would hide
or cover more than a majority of the first bracket.” J.A. 338
(alteration in original) (emphasis added). As the examiner
noted, Figures 13A–B are instructive as to what he meant
by “not passing all the way through.”
Like the examiner, the district court relied on the in-
struction of Figures 13A–B. The district court noted that
when the handle/lever 152 is in the claimed “first rotational
position” as shown in Figure 13A, “the hollowed-out space
defined by the handle” is “bounded on one end by the
rounded, upper portion of the handle, open on the other end
of the handle, and blocked off on the underside by the plane
of the rail.” Summary Judgment Order, 2024 WL 1332027,
at *11 (emphasis added). Meaning, because one end of the
handle is closed off against the rail, “in that configuration,
the hollowed-out space does not pass all the way through
[the handle] in any direction.” Id. Little Giant’s
Case: 24-2115 Document: 55 Page: 9 Filed: 02/05/2026

-- 9 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
10
diagrammatic depictions improperly divorce the handle
from the rest of the locking mechanism portrayed in the
figures and fails to account for what claim 1 requires,
namely the existence of the rail in relation to the bracket
and the handle.7 See Appellant Br. 27. Therefore, we reject
Little Giant’s argument that “not passing all the way
through” needs a directional elaboration.
We also find Little Giant’s argument for “hidden or con-
cealed” unpersuasive. Little Giant previously advocated
for this construction under its proposed construction of the
term “disposed within,” see J.A. 267, and it is not appealing
the district court’s construction of that term, see Appellant
Reply Br. 23 n.9. In any event, neither the examiner’s
statement, the claims, nor the specification support Little
Giant’s assertion. See Summary Judgment Order, 2024
WL 1332027, at *4; see also Claim Construction Order,
2022 WL 2287048, at *9. Accordingly, we affirm the dis-
trict court’s claim construction.
II. Exclusion of Mr. Smith’s Infringement Opinion
We review a district court’s exclusion of expert testi-
mony under the law of the regional circuit, here the Eighth
Circuit. Sport Dimension, Inc. v. Coleman Co., 820 F.3d
1316, 1323 (Fed. Cir. 2016). The Eighth Circuit reviews
the exclusion of an expert’s testimony “under the
7 We reject Little Giant’s argument that the district
court imported limitations from Figures 13A–B. See Ap-
pellant Br. 45–51. The district court referred to those fig-
ures to explain why it rejected Little Giant’s partial
depiction of the figures’ locking mechanism. See Summary
Judgment Order, 2024 WL 1332027, at *11. In any event,
the district court’s reference to the figures was entirely con-
sistent with the examiner’s reliance on those figures to il-
lustrate his meaning of “doesn’t pass all the way through.”
J.A. 338.
Case: 24-2115 Document: 55 Page: 10 Filed: 02/05/2026

-- 10 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
11
deferential abuse of discretion standard and will not re-
verse unless the district court’s ruling is ‘manifestly erro-
neous.’” Bliv, Inc. v. Charter Oak Fire Ins. Co., 159 F.4th
539, 542 (8th Cir. 2025) (citation omitted).
The district court excluded the testimony of Little Gi-
ant’s expert, Mr. Smith, concerning his opinion that
Tricam’s handle on its Speed Lock (shown below) literally
meets the cavity limitation. Summary Judgment Order,
2024 WL 1332027, at *16; J.A. 4544 ¶ 29. According to
Mr. Smith, as shown below, the area under the black han-
dle occupied by the purple bracket constitutes a “cavity”
because that area is a hollowed-out space passing all the
way through in at least one direction but not in every other
direction. Id.
See id. (Tricam’s Speed Lock, annotated).
Little Giant argues that the exclusion of Mr. Smith’s
infringement opinion was erroneous because the district
court erred in construing the claimed “cavity.” See Appel-
lant Br. 52, 54. Little Giant’s argument fails because we
find no error in the district court’s construction.
We also see no error in the district court’s finding that
Mr. Smith contradicted the court’s construction by “essen-
tially reconstru[ing] the cavity limitation to mean any hol-
lowed-out space that does not pass through in every
direction.” Summary Judgment Order, 2024 WL 1332027,
at *15 (emphasis added). Although the claim construction
explicitly stated that “the claimed cavity does not include
hollowed-out spaces that are unbounded on both ends”
such as a “tunnel” or a “taco shell,” Mr. Smith opined that
Case: 24-2115 Document: 55 Page: 11 Filed: 02/05/2026

-- 11 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
12
a hollowed-out space that passes all the way through two
unbounded ends would literally have the claimed cavity.
Id.; see also J.A. 4388, 4989–90. Accordingly, the district
court did not abuse its discretion by excluding Mr. Smith’s
infringement opinion “based on a claim construction that is
materially different from the construction adopted by the
parties and the court.” Treehouse Avatar LLC v. Valve
Corp., 54 F.4th 709, 715 (Fed. Cir. 2022).
III. Summary Judgment
We review a district court’s grant of summary judg-
ment under the law of the regional circuit, here the Eighth
Circuit. Niazi Licensing Corp. v. St. Jude Med. S.C., Inc.,
30 F.4th 1339, 1350 (Fed. Cir. 2022). The Eighth Circuit
reviews a grant of summary judgment de novo. Id. (citing
Wilson v. Spain, 209 F.3d 713, 716 (8th Cir. 2000)). Sum-
mary judgment is appropriate “if the movant shows that
there is no genuine dispute as to any material fact and the
movant is entitled to judgment as a matter of law.” FED.
R. CIV. P. 56(a).
The district court granted summary judgment of non-
infringement, determining that (1) no reasonable jury
could conclude that Tricam’s Speed Lock literally infringes
the cavity limitation and (2) amendment-based estoppel
precludes Little Giant from relying on the doctrine of
equivalents. Summary Judgment Order, 2024 WL
1332027, at *22.
Little Giant offers two arguments: (1) because the
claim construction of “cavity” was erroneous, the summary
judgment should be vacated, and (2) even if the claim con-
struction was correct, the district court erroneously applied
amendment-based estoppel. See Appellant Br. 55–64. We
find both unpersuasive.
A. No Literal Infringement
We begin with the district court’s summary judgment
of no literal infringement. Little Giant’s sole argument
Case: 24-2115 Document: 55 Page: 12 Filed: 02/05/2026

-- 12 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
13
requires prevailing on the “cavity” claim construction. See
Appellant Br. 57 (arguing that “Mr. Smith’s expert opin-
ions raise a genuine dispute of fact regarding the presence
of the ‘cavity’ limitation in the accused [product]” “under
the proper construction of ‘cavity,’ as set forth in Mr.
Smith’s reports”). Because we affirm the district court’s
construction of the claimed “cavity,” the summary judg-
ment of no literal infringement stands.
In any event, the district court did not err in its literal
infringement analysis. The cavity limitation requires that
“more than a majority of the first bracket is placed inside
of” a cavity. Claim Construction Order, 2022 WL 2287048,
at *10 (emphasis added). As depicted below, the Speed
Lock undisputedly has five hollowed-out spaces within its
handle that do not pass all the way through, each space
corresponding to the claimed cavity.8 See Summary Judg-
ment Order, 2024 WL 1332027, at *2–3. However, it is also
undisputed that only 20% of the volume of the bracket is
placed inside of these five cavities; therefore, the cavity
limitation was not met. See id. at *16. Little Giant as-
serted that the Speed Lock handle’s wing space is also the
claimed cavity, thereby satisfying the claim limitation
“more than a majority of the first bracket.” Id. at *16; see
also J.A. 2744. The district court properly rejected Little
Giant’s assertion because it relied on Mr. Smith’s excluded
opinion that a tunnel or taco-shaped structure, which
passes all the way through, satisfies the cavity limitation.
Id. at *17 (further noting that “Little Giant identifies no
other evidence” to support literal infringement).
8 Tricam conceded that Speed Lock has center and
outer cavities as depicted in the right figure. J.A. 48. The
parties, however, disputed whether the wing space meets
the claimed “cavity.” J.A. 51, 2744 (defining the wing
space).
Case: 24-2115 Document: 55 Page: 13 Filed: 02/05/2026

-- 13 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
14
Accordingly, we see no error in the district court’s summary
judgment of no literal infringement.
See Summary Judgment Order, 2024 WL 1332027, at *2–3
(Tricam’s Speed Lock, alongside a labeled image of its un-
derside); see also J.A. 2744.
B. Preclusion under the Doctrine of Equivalents
“Prosecution history estoppel applies as part of an in-
fringement analysis to prevent a patentee from using the
doctrine of equivalents to recapture subject matter surren-
dered from the literal scope of a claim during prosecution.”
Pharma Tech Sols., Inc. v. LifeScan, Inc., 942 F.3d 1372,
1380 (Fed. Cir. 2019) (citation omitted). The Supreme
Court explained that a patentee’s “decision to narrow his
claims through amendment may be presumed to be a gen-
eral disclaimer of the territory between the original claim
and the amended claim.” Festo Corp. v. Shoketsu Kinzoku
Kogyo Kabushiki Co., 535 U.S. 722, 740 (2002). One of the
ways the presumption may be overcome is if the patentee
shows that “the rationale underlying the amendment may
bear no more than a tangential relation to the equivalent
in question” (tangential relation exception). Id. The tan-
gential relation exception “focuses on the patentee’s objec-
tively apparent reason for the narrowing amendment,”
which “should be discernible from the prosecution history
record.” Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki
Co., 344 F.3d 1359, 1369 (Fed. Cir. 2003).
Little Giant challenges the district court’s rejection of
its theory under the doctrine of equivalents that “the wing
space in the Speed Lock handle ‘performs the same
Case: 24-2115 Document: 55 Page: 14 Filed: 02/05/2026

-- 14 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
15
function as the claimed cavity by encompassing more than
a majority of the bracket when in the first rotational posi-
tion.’” Summary Judgment Order, 2024 WL 1332027, at
*17. It argues that the district court erred in two regards:
(1) the Festo presumption does not apply because the Speed
Lock does not fall within the surrendered territory, and
(2) even if the Speed Lock falls within the surrendered ter-
ritory, the tangential relation exception rebuts that pre-
sumption. See Appellant Br. 59–60.
We reject both arguments. First, the district court did
not err in its findings on the scope of the territory surren-
dered. During the ’416 patent prosecution, the examiner
rejected the claim language of “a substantial portion of the
first bracket is concealed between the first rail and the first
component” over a prior art reference U.S. Patent
No. 2006/0169539 (Grebinoski). J.A. 2931–33. In re-
sponse, the applicant amended claim 1 to recite “the first
bracket is disposed within a cavity defined by the first com-
ponent,” which appears in the issued claim. J.A. 2943. In
view of this narrowing amendment, we agree with the dis-
trict court that the surrendered territory is between “de-
signs where the bracket is concealed between the handle
and the rails” and “where it is disposed within a cavity of
the handle.” See Summary Judgment Order, 2024 WL
1332027, at *20. And the Speed Lock handle’s wing space
does fall within this surrendered territory because there
“the majority of the bracket is concealed between the han-
dle and the rail simply because that concealment occurs by
placing substantial portions of the bracket inside a space
that is not a cavity.” Id.
Second, the district court also did not err in determin-
ing that the tangential relation exception does not apply.
Little Giant argues that the amendment at issue was to
overcome “handles that merely conceal part of the bracket
outside the handle.” See Appellant Br. 59–60 (emphasis
omitted). We disagree. Little Giant’s proposed tangential
rationale is not objectively apparent from the prosecution
Case: 24-2115 Document: 55 Page: 15 Filed: 02/05/2026

-- 15 of 16 --

LITTLE GIANT LADDER SYSTEMS, LLC v.
TRICAM INDUSTRIES, INC.
16
history. See generally J.A. 2908–52. This is because, as
the district court found, “the difference between conceal-
ment (or something being hidden between the handle and
the rail) and being disposed within a cavity, was at the
heart of the amendments to avoid Grebinoski.” Summary
Judgment Order, 2024 WL 1332027, at *21. Accordingly,
we hold that Little Giant has not met its burden of proving
that the objectively apparent reason for the narrowing
amendment was only tangentially related to the equiva-
lent.
CONCLUSION
We find none of Little Giant’s remaining arguments
persuasive. For the foregoing reasons, we affirm.
AFFIRMED
Case: 24-2115 Document: 55 Page: 16 Filed: 02/05/2026

-- 16 of 16 --