Abstract: A cap for the top end of a fence post with four sides is provided. The cap has two parts, a base which is designed to fit over the end of the post and which has a locking section on each side consisting of a ramp above the top of the side which slopes downwardly to a locking ledge. The base is attached to the top of the post by nails or screws that extend through a hole either in the sidewall of the base or in tabs that project into the aperture in the center of the base. The top member has a locking bar on the inside of each side that snaps over the locking ledge on the base after sliding down the locking ramp. The top member and base are preferable formed from plastic to have sufficient flexibility to allow the locks to lock, but sufficient rigidity to hold them in the locked position.