Draw a picture or letter on the tile with a pencil or crayon.
Wear your safety goggles and dust mask. Attach the flex-shaft attachment to your rotary tool. This will allow you to hold the rotary tool like a pencil.
Plug the rotary tool in a wall outlet and turn it on. Engrave over the outline of the picture or letter carefully and slowly. Apply firm pressure when engraving to create a noticeable depth in the tile.
Wipe off any small particles and pencil marks left over from the engraving process with a clean, dry towel.