Here's a tool I found useful for marking. Accutrax pencil blade marking knife.



I have one I've been using on and off for a while. Its a fine pencil lead in the shape of a utility blade that can be installed in any utility knife handle and used with a straight edge, combination square, saddle square etc. to mark easily seen, fine lines on wood..

Here's mine. I have not broken it, it seems to be quite sturdy. The sharp edge lasts a long time. I'm still on the original blade and it came with a pack of 5 and like utility blades, can be reversed when too worn. Being in a knife handle, its perfect to mark with just as you'd cut a piece of paper or cardboard.
Never needs sharpening, extend it as it wears with the blade retractor of the knife handle. Much sturdier than a mechanical pencil lead for marking on rough or uneven wood.