Measure the height on your wall where you want to install your granite corner shelf.
Measure the dimensions of the part of your shelf that will be fitted to your wall. Then, using a wall tile cutter, create a hole in the tile on your wall to form a space to fit your shelf. Make the hole you cut 2 inches shorter than the length of your shelf on the walls along both sides of your corner.
Notch the 2 inches at the end of the lengths of your shelf so they'll fit into your hole. You'll need to use a circular saw with a purpose-made diamond blade. Wear safety goggles while you're cutting your shelf.
Slot your shelf into the hole in your wall to make sure it fits. If it doesn't, trim its shape with the circular saw.
Apply 100 percent silicone to the back of your shelf and push it into position in the hole in your wall. Use plastic wedges to secure it in place.
Let the shelf dry for at least 24 hours.
Remove the plastic wedges securing your shelf in place and apply silicone to the joint between your wall and your shelf. Smooth the silicone into place with a wet finger and wipe away any residue with a damp cloth.
Allow the silicone to dry for at least 24 hours before exposing your shelf to water.