EASY & Agrave; USE Center pilot tips are for wood, metal, etc. Here is how you can keep the drill bit on target: a- You can make your own plywood guide; - plastic or even cardboard. You just need to hold the bit in place until what it marks the initial marks. b- It is possible to start drilling at an angle, with the edge of the bit forming a C-slot and then bringing the bit vertically. c- You can manually guide the bit with a wet sponge.Package Included: 1*Diamond Drill Bit SetDescription: Applicable Industry: Suitable to the processing of stone, tiles, ceramics, glass and granite, etc. Silver color Quantity: 15 pieces Feature: The electroplated diamond coating wears out if the tool overheats. Never let the bit dry out. Here's how to use water to cool the tool: a- You can build a mini water dam around the hole with plumber's grout. b- You can choose to spray water on the tip. c- Or you can use running water to cool the bit. Note: Start your hole diagonally, make a round track then keep the drill straight. Drilling pressure and the increased use of lubrication at the bottom. water will greatly extend the life of the drill. Speed Kills: Reduced drilling speeds, low drilling pressure, and increased use of lubrication at the bottom. water will greatly extend the life of the drill. Warnings: Do not use on concrete or for depths greater than approximately 1/2"; water is required for drilling for lubrication.