The wide swivel mounts on the forend of the fullstock and should be positioned to rest against a ramrod pipe body. The screw should be installed through a underlug dovetailed into the bottom flat of the barrel such as a #UL-DH-1, sold separately. Uses a 6-40 screw, included with the swivel. Order #SCREW-UL-6-40, if you need a replacement. Swivel is 15/16" wide inside dimension at the mounts.