A holder for capillary columns is realized by a mechanical holding device, also called a lead holder, which can be a mechanical pencil. The constraining structure can expand to form a pattern of channels including substantially square windows. This system is useful when applied in developing a control program to be embedded in a mechanism, such as CD changer, MD changer, printer or manipulator, which includes at least an actuator and a sensor and produces a three-dimensional motion. The feet are formed with upward projections that are gravitationally engaged into voids formed in the bottoms of the modules to lock the side members in position at the sides of the modules. The layer 13 is a liquid crystal layer formed by curing a liquid crystal composition comprising a polymerizable liquid crystal material. The coupling mechanism operates to extend a coupling bar from the model car when the train turns to the right or left, providing clearance for further rotation of the bar.