Water supply shut-off valve
Tear a small piece of emery cloth from the roll. Clean the outside of the copper water-supply pipes and the inside of the shut-off fitting with the emery cloth. Rub the emery cloth against the pipes and fitting until the metal shines.
Brush a coating of flux around the cleaned pipes and fitting with a flux brush.
Assemble the shut-off valve. Insert the ends of the pipes into the openings of the valve. Twist the valve to lightly spread the flux.
Light the torch with a spark starter. Hold the torch's flame over one of the joints between the valve and water-supply pipe. Heat the joint until solder melts when pressed against the copper pipe.
Remove the flame from the joint. Press solder into the joint and allow solder to flow into the joint until a ring of solder squeezes out from the seam between the pipe and the valve. Wipe excess solder from the pipe's surface with a wet rag.
Apply the torch's flame to the opposite joint and heat the joint until the solder melts when pressed against the pipe. Remove the flame from the joint and press solder into the joint until a ring squeezes from the seam. Clean the joint with a wet rag.
Gas shut-off valve
Wipe the male threads of the gas supply pipe with a clean cloth. Remove traces of dust, old pipe dope or thread-seal tape from the pipe's threads.
Use the brush mounted to the underside of the pipe dope's cap to apply a coating of pipe dope around the external threads of the gas supply pipe and the internal threads of the gas shut-off valve.
Press the internal threads of the shut-off valve against the external threads of the supply pipe. Twist the valve clockwise while applying gentle, forward pressure to engage the threads. Tighten the valve onto the pipe until hand-tight.
Attach a pipe wrench to the supply pipe and an adjustable wrench to the valve's hexagonal collar. Grip the pipe wrench with one hand and the adjustable wrench with the other. While holding the pipe wrench in place to stabilize the pipe's position, turn the adjustable wrench to finish tightening the valve.