Structures for transitioning between two layers of differing lattice parameters are disclosed. The brachytherapy device has at least one source lumen located outside a movable surface of the device. Each of the lids has a main panel section, a perimeter skirt assembly around the main panel section, a top side, and a bottom side. The gear box is arranged and constructed to transmit motion to the output member in response to the activation of the elongated operating member, at a predetermined mechanical advantage.