From DIYinfo.org
[edit] It Simple When You Know How
Scribing with a marking gauge (fig. A) often saves a great deal of laborious measuring and marking. Marking gauges are cheap and make life easier when marking out joints.
The techÂnique takes a bit of practice to master, so you should experiment on wood off cuts before starting any serious scribing work.
To scribe a mark, arrange the, work piece with the gauge nearest you. Make sure that the sliding block is flush against your face side or edge, then roll the gauge towards you until the needle touches the, wood (fig. 3).
Keeping the gauge at this angle, run it away from you down the work piece to scribe the line.
Avoid applying excessive pressure as you do this: if the needle digs in too far, a wavering line will result.
To scribe a line down the middle of a work piece, set your marking gauge to roughly half its width and make a mark from the face edge.
Make a mark from the opposite edge in the same way, adjust the gauge, then continue making marks from either edge until the two marks coincide.




