What is a stab in an electrical panel?

A stab is a way of connecting an external electrical device to a distribution bus bar. Stab lok breakers have a stab that connects the breaker to the bus bar by pushing the breaker into the bus bar and the breaker stab applies pressure in four directions to secure it. Another device that uses a stab is a module (bucket) that fits into a MCC (motor control center). These stabs are movable and are used to align the module to the bus bars. Using stabs on these devices allows for expansion and contraction of the bus bars when heavy loading generates heat. Also individual modules can be removed from the MCC without shutting the entire MCC off.