To select the correct depth of tile trim for your tile you should use a tile trim one size up from the depth of your tile. For example if your tile is 10mm think use a 12.5mm tile trim. This will allow for the adhesive needed to hold the trim and tile in place.
The holes in the back of the tile trim allow adhesive to pass through them. When the tile is placed on top the adhesives spreads out holding the tile and the trim in place. Remember to clean any excess adhesive off the face of the tile trim and tile before the adhesive dries. Our range of tile trims can be found here.