A classic carpenter pencil with a hard core and plenty of barrel to protect it.
Carpenter pencils are flat so they don't roll and unlike general writing pencils, the can survive a few falls without the graphite shattering inside the wood.
The Field Notes 7" Carpenter Pencils fit nicely in your overalls pocket, or behind most standard human-size ears. The new ridiculously-bright fluorescent orange coating makes them easy to find in a cluttered workshop or toolbox.
