I do a fair bit of layout work with a pencil. I find it’s a quick way to figure things out on a unique project, or a unique piece of wood that you want to get all the cuts “just right”.
Normally, I use a combination square as a pencil gauge when I am trying to get the width of a workpiece. As it happens, both my combo squares had settings I did not feel like losing, so I borrowed a very old carpenters trick.
Holding your hands like this you can use a rule to mark out a line that will easily be within a 16th of an inch of where you want it. Just slide the whole works down the board to mark out your width (notice how my finger is riding against the edge of the board…that’s the depth stop).
-- Make furniture that lasts as long as the tree - Ryan