Bathtub backsplash protection is similar to a rear wall behind the sink in the kitchen, with the exception that generally goes all the way around the tub, instead of behind the faucet. In a standard configuration bath, you will have three walls behind the tub, and they must be protected. The motherboard can go so far up the wall, or all the way to the ceiling, depending on your personal preferences. If there is an enclosed shower in the tub, tile should go all the way to the wall.
Measure across one wall above the bathtub backsplash, on the edge. Mark the center. Mark a vertical line to the wall in the middle with a pencil and level, taking the top line that you want the splash guard to go.
Make a horizontal line all the way around the walls above the bathtub at the height you want the bathtub backsplash guard to come. For the splash guard to cover the entire wall to the ceiling, you can skip this step. Use a notched trowel to spread adhesive cement along the wall of the rim until you drew the line marking the top of the protection zone or ceiling splash bath.