This is a top mount bi-fold door pivot and guide. Used by a variety of door manufacturers, the 7/16 inch pivot cap on the spring-loaded pivot pin inserts into the 3/8 inch spring-loaded pivot pin is housed in a 3/8 inch nylon base. The pin installs into the top bracket creating a top pivot point for the bi-fold door. It may also serve as a guide for the lead door as it slides back and forth in the track. See Prime-Line part N 6837 for the pivot bracket.