Hi Carol, Thank you for your question. There are 2 ways that you can install the 55011 wall mount hand shower. The first way is to install a 3 way shower arm diverter like model U4923-PK on the shower arm of the faucet you select then attach the fixed showerhead and the handheld showerhead to the diverter. All of this is done on the outside of the wall. In the second choice the plumbing connections are made behind the wall. You will select your faucet trim, and R10000 rough in. Next you will need a 3 setting diverter trim and R11000 rough in. Finally you will need a wall elbow like model 50560 and the 55011 to complete your desired installation. The diverters in both installations will allow you to use each showerhead individually or at the same time.