The Locking Knob is a must have for any Hi-Lift manufactured Jack Mounting Kit owner. The Locking Knob replaces an existing knob or wing nut provided on Hi-Lift Jack Mounting Kits. Once tightened, the Locking Knob can be locked with provided key. Once locked, the Locking Knob spins freely and cannot be removed, securing the Hi-Lift Jack. The Versatile Locking Knob is made for use with 4XRAC, Adjustable Tube Mounts, and Loc-Rac. The Versatile Locking Knob can also be used to secure the Winch-Clamp-Spreader Attachment that is only available on Hi-Lift X-TREME Jack models.