Embodiments of the present invention are directed to methods and system for conducting transactions for a self-checkout system. The SID of the base station seized when the apparatus was turned off last is stored in the apparatus, too. A control ferrule may be slidably engaged onto the shaft to selectively retain the tool member in line with the shaft and to prevent the tool member from being tilted relative to the shaft, or to allow the tool member to be slanted and tilted relative to the shaft to different angular position. The contacting portion is formed from tungsten.