A junction/outlet box locking insert, system and method including an insert body with an outer insert body surface and an inner axially extending pass through region having an open end and an end with an electrical cable/conduit stop with a central electrical conductor pass through opening. A retainer flange is connected with the insert body at an axial end thereof. An insert stop device cooperates with the retainer flange for fixing a position of the insert body relative to a junction/outlet box. A locking finger arrangement is connected to the insert body and includes a locking finger extending radially inwardly of the outer insert body surface. The locking finger is self-actuating for engaging a conduit or a metallic sheath of an electrical cable upon the conduit or a metallic sheath being inserted into the pass through region up to the electrical cable/conduit stop.