The Rock-cutter is a device used by the Sidhe to work with stone and other dense materials.
They are black cylinders, about a foot (30cm) long, with two couple of indentations on the main body that are the only controls and a series of concentric rings that appear to be fashioned from glass at one end. They have two known modes of operation; cutting and welding. Depending on how the device is held dictates the mode, but the pressure applied to the controls allows the operator a high level of control over the power and size of the energy beam directed at the target.
The device also feeds back information about the cutting process to the operator, so that he or she becomes aware of harder or softer material and can adjust the power accordingly.