A tool suspension plate has a base, at last one fastening device formed on the base, and a slat detachably mounted on the base to cross over the at least one fastening device and to secure at least one screwdriver on the base. In the casting step an iron casting having a spiraling part is formed. A computer is provided to control movement of the movable picking arrangement according to an order sequence. The first and second interengagement features are dimensioned to cooperate with one another to operatively provide a non-visual indicator of a positive interengagement between two wall panels. Specifically, several connectors are coupled to one connector so as to be electrically connected to it, thereby concentrating the connector assembling processes in an in-line assembly line at one place and enhancing production yield andor production rate.