Fine 'tune' drill bit angle using a CD
To drill perpendicular holes with a handheld drill, here's an inexpensive solution. Grab a compact disc (scratched ones that won't play work just fine for this) and center it on the hole mark. As you drill the hole, watch the reflection in the CD—keep the bit in a straight line with its reflection for a perpendicular hole every time.
—Robert Heil, Wheeling, W.Va.