These clip on sign holders are used with threaded stems. The clamp is ideal on the sales floor because of it ease of application. These clip on sign holders are great for placing signage where it will be visible. The clamp eliminates the need for thumbscrews or bolts. The sign holder will be great for organizing the sales floor. Heres how the system works: 1) Choose size and style of frame that best suits your sign. 2) Decide which type of clamp will work best for your fixture: magnetic, spring, or C-clamp. 3) Complete the holder with the appropriate stem fitting and length.