This Accessory Mounting Post allows you to mount any accessory that has a 1/4-20 female thread. They are available in 1.5" and 2" lengths. The 1/4 20 captive screw helps to keep you from losing your knob and makes it much easier to use. It has the same high quality fluted knob that is used for camera knobs, but with a longer screw. The screw extends .25" past the end of the rod.