Abstract: A deadlock mechanism comprises a casing having a facing plate provided with a bolt aperture and a bolt movable through the aperture between an unlocking position and a locking position. This bolt is connected to a reciprocable plunger, the bolt being made up of a pair of levers each having a locking ear at its forward end and a camming lug at its rearward end, the rearward ends of the levers being pivotally mounted at the end of the plunger so as to pivot in opposite directions when the bolt moves out of the casing into locking position. Movement of the bolt and pivoting of the levers as they move in and out of the casing is obtained by the coaction of camming edges on the levers and cam followers within the casing.