Anyone who is familiar with old-school, hand mechanical drafting would probably know this one. In this day and age, however, with all the available forms of CAD software, this technique has gone the way of the rotary dial telephone.
The idea is simple: maintaining a very sharp tip on your marking pencil.
By keeping a sheet of fine grit sandpaper on the workbench, one can stop frequently during marking operations to sand a sharp chisel tip into the pencil lead.
This has two benefits:
First, the sharpened tip can produce an extremely thin, precise mark or line. This is highly useful to those who build scale models, where utmost precision is required.
Second, the chisel tip can be butted up extremely tight into the right angle formed by the part surface and straight-edge. No pencil-lead width errors are introduced that might throw off a precision measured line.
This technique can be used with normal mechanical pencils using #2 lead. They just have to be sharpened more often.
Harder leads such as number 4 or 5 are better, as they will hold a sharp edge longer, though producing a lighter line.
