A scalpel has a handle and a blade carrier 2 movable within a longitudinally extending cavity between an operative position in which a blade on the blade carrier 2 is exposed for use and an inoperative retracted position. A manually operable slider 4 moves the blade carrier 2. The carrier has a catch face 21 directed rearwards in the operative position which partially aligns with a stop face 11 provided on the handle so force exerted on a blade in the direction of the length of the handle causes engagement of the catch face 21 with the stop face 11 to arrest movement of the blade carrier 2 into the cavity. Transverse biasing of the blade carrier 2 is overcome by pressure exerted on the slider 4 to retract the blade carrier 2 into the handle with the catch face 21 passing the stop face 11. The catch face 21 may be on a cantilever arm. The transverse biasing may be by means of a squat closed loop leaf spring 25.
