An apparatus includes a shaft, a slide lock, and a pin. The shaft includes a first end, a second end opposite the first end and a middle portion between the first end and the second end. The first end includes an
enclosure. The middle portion includes a tapered hole. The tapered hole is tapered in a direction from the first end to the second end. The slide lock is disposed over the shaft. The pin is disposed through the tapered hole and coupled to the slide lock. The movement of the slide lock is coupled to movement of the pin within the tapered hole of the shaft. The position of the pin within the tapered hole corresponds to an amount of opening of the
enclosure.