2 hooks suitable for printing in most rigid materials. The cam slot has 2 sets of retainers internally to grip most materials. Works well printed with 0.4mm nozzle with 0.2mm layer height. Solid infill is recommended for strength. 

The photo shows intended use. If your cloth does not have a hem, fold it to make one. There are double interlocking ribs running the length of both sides of the cam. the “teeth” prevent it sliding back out accidentally.