A. If the trim ring (escutcheon) fits snug onto your shower arm and stays in place close to the wall then you usually do not need to seal around it. Most shower heads fall below the shower arm where it exits the wall and thus maybe only an occasional water splash may come in contact with the escutcheon, and in those instances it will protect the wall opening from water. If you are using an extension type shower arm and the head is above the escutcheon then you may need to seal around the trim ring to protect the possibility of a spray of water deluging the escutcheon area. If you do wish to seal around the escutcheon then only seal the the top two-thirds of the escutcheon and leave the bottom one-third open. In this way if some water does get behind the wall escutcheon it has a way to get out.