Step-by-step Start by removing the existing faucet handles, escutcheons, showerhead and tub spout. Look for a hex-head set screw on the underside of the tub spout. Loosen it with a hex-key wrench and pull the spout straight out. If there is no screw, the spout is threaded on. Cover it with a cloth and twist it off counterclockwise with a pipe wrench (photo 1), or insert a wood plunger handle in the spout itself and turn it counterclockwise. Next, cut an opening in the back side of the plumbing wall with a drywall saw (photo 2); gently pry out the piece and save it. Go from stud to stud (about 141/2 in. wide) and from 6 in. above the faucet handles to 8 in. below the tub spout. Keep in mind that a larger wall opening makes it easier and safer to solder; what's more, it's no more difficult to repair than a smaller opening. Shut off the water to the tub and shower and cut out the old faucet with a hacksaw or miniature tube cutter (photo 3). Next, move around to the tub side of the wall to enlarge the two handle holes (photo 4) for the Monitor II valves. Cut the right-hand hole to 3 1/2 in. dia. and the left-hand hole to 21/4 in. dia., making sure the enlarged holes measure 8 in. from center to center. Threaded inlet and outlet ports on the Monitor II accept 1/2-in. male adapters, which have to be soldered, or sweated, onto copper pipe. But to keep from scorching the neoprene and nylon cartridges inside the valve, solder the adapters onto short pipe lengths, called stubs. Allow the fittings to cool completely and then thread the adapters into the ports. Make all the stubs at least 8 in. long, except the one for the tub spout. It must be cut exactly to length: Set the valve assembly into the wall openings and measure down to the hole for the spout.