Abstract: An electric circuit breaker panelboard equipped for lug main connection (22,24) and having a plug-in main circuit breaker (26,28) held securely in place by bracket (36) secured to the panel (2) by a screw (38) and having a forward hook (36c) overlying a forward edge (26c) of an insulating barrier adjacent the load side connector (26b) of the breaker. The bracket (36) has a ledge (36d) overlying a mounting rail (2b) on the panel (2) in position below the hook portion (36c) such that movement of the breaker (26,28) in a direction to cause separation of the plug-in electrical connection thereof with the panelboard exerts a bending on the bracket and a compressive force on the mounting rail to resist such movement. The bracket is colored red to be clearly visible and serve as a warning against removal of the main breaker under electrical power.