Abstract: This invention discloses an electromechanical bolt assembly for locking a door. A bolt, which is retracted when a solenoid is energized, moves a lever assembly which causes a latch trigger to extend into the doorway. The bolt is held in the retracted position by a detente while the door remains open. When the door is closed, it depresses the latch trigger, which operates the lever assembly, causing the bolt to disengage from the detente and extend into the locked position. This locking mechanism is well suited to high-security environments such as prisons. It is highly durable, and can be contained in a housing which allows for simple and convenient installation.