Medical devices include a ground link, a first actuator pivotably coupled to the ground link and a first movable element operatively coupled to the first actuator by a linkage. The linkage including: the ground link; a second link that is pivotable with respect to the ground link; a fourth link that is pivotable with respect to the ground link; and a third link having a main body extending from a first portion to a second portion and a blocking tab extending away from the main body. The medical device further including a second actuator operatively coupled to the ground link, the second actuator having a blocking surface including a blocking tab that is positioned to engage with at least a portion of the blocking surface of the second actuator to limit movement of the second actuator until the first actuator is at least partially actuated.