PIERCE twist lock plunger pins are used on applications where a self-locking mechanism is needed. Traditionally, plunger pins are used in the towing field on wheel lifts and wrecker slings. Activate by rotating the head. They are easily welded into position for maximum versatility. The design incorporates a protective shoulder to prevent binding when welding the plunger into place. Use on sling arms, wheel lift arms, dump kits, etc. Drill a 3/4″ hole then weld the pin into the space. Grease the pin regularly for optimal performance.