Program a machine that applies acid to precision-etch metal and plastic.
Strings tennis and badminton rackets with synthetic fiber or animal gut strings: Clamps racket in stand and threads warp through holes in bow. Clamps ends of strings in jaws of tensioner arms, depresses pedal to tighten strings to prescribed tension, and locks strings in place by wedging awl in hole with string until next set of holes are strung, or string is tied. Threads weave through holes in bow, weaves them through main strings, applies tension, and secures them similarly to main strings. May wrap bow at intervals with bands of colored thread to strengthen and decorate it. May varnish wooden parts of racket. May replace leather or plastic grips on racket handle.