Code Required Mechanical Hold-down For Installation of Murray MP2100 As A Replacement for Crouse-Hinds MP2100 Main Circuit Breakers. The Original MP2100 Crouse-Hinds Main Had a Thru-hole That Received A Bolt That Bonded The Main To The Load Center Interior. The Current Model UL Replacement MP2100 Does NOT Have The Thru-hole So This Device Is Snapped Onto The Load End Of The Breaker To Mechanically Bond It To The Interior. Qty 1 Per Bag