In one embodiment, a surgical instrument includes a first and second lever arms coupled by a first pivot. A ratchet bar is coupled to the first lever arm by a second pivot. The ratchet bar has a toothed portion extending from an interior face of the first lever arm and a paddle portion extending from an exterior face of the first lever arm. A catch is disposed at a proximate end of the second lever arm and arranged to engage teeth of the toothed portion of the ratchet bar. Engagement with the teeth couples the proximate ends of the first and second lever arms. The ratchet bar is further arranged to rotate about the second pivot in response to downward pressure upon the paddle. Depression of the paddle causes the teeth of disengage the catch, decoupling the first and second lever arms.