A sliding board, such as a ski, with at least one interface element or guide element, connected to the sliding board via fastening elements, for arranging binding elements or the like on the upper side of the sliding board. A plurality of conveyor rails are attached to a conveying device at a predetermined space and carried along an endless track. The polymers may be employed in medical devices and are useful for instance to track the movement of a catheter through the body or the inflation of a balloon at a site. Also disclosed are methods to optimize the size of the buffers to minimize bottlenecks. The flag variables are used for recording execution progresses of the sub-operations. The first message is detected when the first data has a finish flag and an acknowledgement flag which are set, and the second message is detected from the second data responding to the first data and having an acknowledgement flag which is set.