*Also, just to add that when you break the casing off it lets you take a paper clip and move the trip piece back simulating an over load. The arm will release but get hung up on the internal common trip lever preventing that arm from going down. What made me do this in the first place was when a MWBC fed from a double pole handle ties removed breaker inadvertently short circuited while the other pole was turned off. The pole left on never tripped despite carnage saying it should have.