This is a top mount bi-fold door pivot that is typically used on Alliance bi-fold doors. The spring loaded 1/4 inch steel pin inserts into a pre-drilled hole in the door and a top bracket above, creating a pivot point for your bi-fold door. Each steel pin is self-adjusting and features a mold injected clear plastic base. No fasteners are required for installation, but a soft mallet can be used with caution.