A handle of a medical device may comprise an actuator; a lock movable relative to the actuator and having a feature movable relative to the actuator; and a rack having plurality of teeth separated from one another by a plurality of gaps. The lock may be configured to move the feature from (a) a first configuration, in which the feature is disposed in the gap, between two of the plurality of teeth, such that the two teeth inhibit the actuator from rotating; to (b) a second configuration, in which the feature is disposed outside of the gap, such that the actuator is rotatable. In the second configuration, the teeth may be disposed between the feature and the actuator.