Abstract: A surgical instrument having an elongate body includes an operative section at its distal end and a operating section at its proximal end. A pair of scissorshandles form a handle assembly in the operating section and are operable in a normal plane of operation to control the operative section. A ratchet assembly including a ratchet pawl and a series of ratchet teeth is enclosed within the handle assembly to avoid contamination by debris. The ratchet assembly can be engaged and disengaged with forces limited to the natural plane of operation; no unnatural lateral forces are required. A portion of one of the handles is moveable in the plane of operation in a first direction to engage the ratchet assembly and is moveable in the plane of operation in a second direction to disengage the ratchet assembly.