Draw studs are also known as piston shafts, draw screws and punch shafts. Manual or ratchet and hydraulic versions are available. Manual or ratchet draw studs have hex (bolt) head and thrust bearing. Hydraulic draw studs are threaded on both ends. The screw or stud is screwed into the punch unit through the sheet metal or material to be punched while the other end threaded to the the punch (of the punch and die) screw tightened or hydraulically pulled until the punch is completely drawn through the sheet metal or material.
Alternate terminology: Knockout Punch Draw Studs, Punching Piston Shafts, Threaded Punch Shafts, Punch Draw Screws.