One of the things that fine woodworkers commonly do to get better accuracy in their craft is to get rid of their pencils. Pencils get dull, are difficult to see on many woods, and the thickness of the line varies with the level of sharpness and angle of use. All in all, they're just not an accurate way to mark out detailed work.
That's why instead they use a "marking knife". Basically a knife with a very sharp point that is only sharpened on one side. (That way the back is flat to ride against the ruler, square, or whatnot.)
The problem is that these knives generally cost between $10 and $50, and a good toolbox would be stocked with 2-3 of them. (Left, right, and ambidextrous)That certainly adds up! (Here's an example from a popular catalog for comparison.
The solution I came up with is not only made 100% free using stuff you'd normally throw in the trash, but the blades are replaceable, the handle is nice and big for people with arthritis, AND the whole thing can safely go with you in your pocket!
So what's the big secret, then? Re-engineer your spent utility knife blades!!!