Using reflection
The use of reflection is a wonderful aid to the hand tool woodworker. I use the reflection of the work piece in my saw plate all the time to ensure that I am sawing perpendicular and vertical. Often I don’t even bother marking a line to follow, because a reflection in flat surface can’t be wrong. So you could say, I had high expectations of this technique. Here’s how it works:
Get yourself an old CD or DVD and tape it down to you work piece (you might have to enlarge the center hole a bit) When you are drilling vertically or horizontally, the reflection will continue in a straight line.