Abstract: A wheel pack and fence utilized to form a radiographically secure combinan lock are disclosed. The wheel pack includes three or more wheels. Each wheel of the wheel pack has a plurality of gates formed in the wheel. Half of the plurality of gates on each wheel are cut halfway through on one side and the other half of the plurality of gates are cut halfway through the other side. The gates are cut in the shape of right triangles and are so positioned that the hypotenuse of each triangular gate on one side of a wheel intersects the hypotenuse of a triangular gate on the other side of that wheel. The fence which must drop into a gate of each wheel to withdraw the lock bolt is designed to contact only one-half of each wheel of the wheel pack. The fence is shaped to fit into a triangular gate of each wheel that is identical in shape and orientation to the fence. There is only one gate on each wheel that matches the fence and therefore there is only one true gate on each wheel.