What is...a form of IP that protects an ornamental design of a functional item? Design Patent.

A Design Patent.⠀

Much like a utility patent, a design patent is a negative right that does not allow you to do anything. Rather, it allows you to stop others from making, using, or selling what your patent claims cover without your permission.

A design patent covers ornamentation, not functionality.

Functionality is covered by a utility patent.

A design patent in the US lasts for 15 years from the date it is granted.