The Screw Tab Cap or table cap PVC fitting is useful any place you want to secure pipe to a surface. Three tabs with screw holes come out from the caps. These are strong when pulling straight out from the attached surface but they are weaker when side to side pressure is applied. Some people use them for mounting a small table to the end of PVC pipe or creating an attachment point for a pipe on a wall. The outlet is a non-threaded socket and is compatible with furniture grade PVC pipe or standard PVC pipe from a hardware store.