Building the shelf

• 1). Take two pieces of the surface tile. Using the margin trowel, apply a layer of mastic or thinset on the back of each piece of surface materiel. Stick them together and apply pressure so that the bonding agent oozes out the sides. Let dry for a minimum of 24 hours.
  
  
• 2). Determine the size of your shelf. You can adjust the size if you find it too big or too small. The grease pencil will allow you to erase your lines and re-adjust until you are comfortable with the size. Using your speed square, set it against the factory edge of the two pieces you glued together and draw two 45 degree angles towards the center of the tiles, so you have a triangle that is of a size you are happy with.
  
  
• 3). Using the wet saw, cut along the two lines you drew using the grease pencil.
  
  
• 4). Clean any excess thinset/mastic from the edge of the shelf that will face into the shower. This is the factory edge, as the two edges you cut on the saw will be nestled into the corner and out of sight.
  
  
• 5). Dry completely.
  
  

Installing the shelf

• 1). Determine the height of the shelf. This will be an area at which you are comfortable with the shelf being.
  
  
• 2). Using your margin trowel, apply thinset/mastic to the edges of the shelf that will go into the corner. Push it into the corner resting on the top edges of the row beneath at the height you chose. Jiggle the shelf slightly in each direction to insure proper coverage of thinset/mastic.
  
  
• 3). You will need to notch the tiles on the wall around the shelf. This is to insure the shelf remains firmly locked in place by the surrounding surface tiles. Use your grease pencil to mark the tiles that will be installed above the shelf. These will be "L" cuts made on the wet saw.
  
  
• 4). Install the notched tiles above the shelf. The shelf is now effectively locked in place.
  
  
• 5). Clean excess thinest/mastic, continue installation of surface tile, and grout the shelf in place when you grout the rest of the shower. You can fill the gap between the two tiles with either grout or caulking.
  
  

If shower is pre-existing

• 1). Take several quarters. Slot them half-way into the edges of the shelf that will be facing the corners of the shower. Two or three quarters per edge will be fine.
  
  
• 2). Using an epoxy adhesive, glue quarters in place. Make sure half of each quarter is sticking out. Let epoxy dry.
  
  
• 3). Remove grout from the horizontal grout lines in an area where the shelf will feel comfortable for you.
  
  
• 4). Using the epoxy adhesive, you can side the quarters into the grout lines between the tiles, effectively locking the shelf in place. Let dry for 24 hours.
  
  
• 5). Caulk the shelf in place.