1. Mark back of the glass tile where you plan to drill a hole. Place the tile on a scrap piece of MDF board with the backside facing up. Align the drill bit with the reference mark and drill a small pilot hole.Flip the tile over.. Take a ball of plumber's putty and knead it into a 1/2-inch-diameter, 10-inch long roll. Join the ends of the putty to make a circle and place it around the area where you will be drilling. Press the circle of putty onto the tile to form a seal. This acts as a temporary dam to hold water while you are drilling.