The "U" shaped swivel mounts on the forend of the fullstock and should ideally rest against a ramrod pipe to prevent blocking the ramrod channel. 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. Swivel is over 15/16" wide inside and will look great on a Jaeger, or Germanic influenced Longrifle.