Many Bathtub Faucets come with a non reusable plastic material dish that is expected to be cleanse with the completed walls area.the tub sink cut dish will not closure properly. Try to do what the designers of old did. Install an accessibility board on lack of of the walls behind the tub or Shower Faucets. This was very typical years ago, and accessibility sections can still be found within wardrobes of many an older home. The accessibility board should increase one foot above the top of the faucet and all the way to the floor.