A grub screw is designed to be screwed into a threaded hole to join two pieces of material. The screw is headless and slotted at one end for a screwdriver. The screw exerts compression force through the bottom tip that projects through the hole to hold the two pieces together.
A grub screw is manufactured of hardened metal, and they come with different head sizes and shapes. The bearing point on a grub screw has various configurations such as cone, oval, flat or cup. A grub screw is inserted into position by an internal hex, Allen, slot, Torx, star or Phillips screwdriver.