A clamp has an open state for inserting an object from a front end and a closed state for holding the inserted object relative to a back end. The clamp includes a frame as well as a first arm and a second arm that is positioned within the frame. At least one of the first or second arms is pivotable relative to the other along a range of motion that traverses an open position corresponding to the open state of the clamp and a closed position corresponding to the closed state of the clamp. In one embodiment, at least one of the first and second arms are shaped to position the object between a front end and a back end when the clamp is in the closed state such that a pressure exerted by insertion of the object to the backend causes the front end to move along the range of motion to the closed position. A locking mechanism locks the clamp to the closed state when the front end reaches the closed position and unlocks the clamp to the open state by allowing the front end to move along the range of motion to reach the open position.