How To Finish Shower Niche Edges . Bullnose tiles will have one side that is curved to provide a finished edge so that the rough side of a tile is never seen at points where the tile stops and the wall starts or in situations like a seat in the shower or a shelf/niche in a. Please don't use mastic in a wet area. Milk Chocolate from www.schluter.com Schluter chrome trim profile and porcelain carrara tile.peygran leveling system: Tiling a shower niche requires a lot of precision. Position with least likelihood of moisture.