## Facts

- Best Lock Corporation manufactured and sold locks and keys for institutional, commercial, and industrial security.
- Best owned U.S. Design Patent No. D327,636 covering the design of a key “blade,” the portion of a key inserted into a lock’s keyway.
- Ilco Unican Corporation sold competing key blanks.
- Blank key blades are made with a specific profile so they will fit a corresponding lock keyway and are later cut to match the lock’s combination.
- In the replacement-key market, sellers stock different blank profiles and select a blank by matching the blade profile to the lock’s keyway.
- Best also had protection covering the corresponding keyway design intended to mate with the claimed blade profile.
- The parties did not dispute that, to function, the accused blade had to have the patented profile to fit the corresponding keyway.
- The district court held the design patent invalid as functional (not ornamental) and entered judgment for Ilco; Best appealed.

## Issues

1. Whether the claimed key-blade design was “ornamental” under 35 U.S.C. § 171 or instead dictated by function because it was required to fit a matching keyway.

## Decision

- The Federal Circuit affirmed the judgment that the design patent was invalid.
- The court held the district court did not clearly err in finding the claimed blade profile was functional and therefore not ornamental.
- The court rejected Best’s argument that the existence of many possible blade/keyway pairings made the particular claimed blade design ornamental.

## Legal Principles

- A design patent under 35 U.S.C. § 171 is valid only for a “new, original and ornamental” design; a design dictated by function is not protectable as ornamental.
- In assessing functionality, the focus is on whether the appearance of the claimed design is required to perform the article’s intended purpose, not on whether other hypothetical designs could have been chosen at the outset.
- For interfitting mechanical parts, when the claimed shape is necessary to mate with a corresponding part so the system works—particularly where the patentee controls the mating configuration—the design is likely functional rather than ornamental.
- Appellate review of the district court’s functionality finding is for clear error.

## Conclusion

The Federal Circuit upheld invalidation of Best’s key-blade design patent because the claimed profile was necessary for the blade to fit and operate within the corresponding keyway, leaving no protectable ornamentality under § 171.


Best Lock Corp. v. Ilco Unican Corp., 94 F.3d 1563 (Fed. Cir. 1996)