Whether you use an open hook or a snap hook, both will attach to this ring. This is the mounted ring where the rope hook attaches. A cool thing about this piece is that the actual ring can be rotated 180 degrees by loosening a screw in the back, moving the ring to orient vertically, horizontally, or any point in between and re-tightening the screw. The inside diameter of the ring is 3/4". The plate is approximately 1 1/4" x 2". Also included with this part are the flat head wood screws...