Swanson "AlwaysSharp" Refillable Carpenter Pencils are very handy. The pencil never has to be sharpened. It always maintains its length—so it won’t get lost in your tool pouch. The lead will also last 5 times longer since there is no waste due to sharpening. See here for Swanson Mechanical Carpenter Pencil Refills.
Product Overall Length Model # Swanson Mechanical Carpenter Pencils - 2 Pack 7" CP216
For California Residents:
WARNING: Cancer & Reproductive Harm - www.P65Warnings.ca.gov
WARNING: Drilling, sawing, sanding or machining wood products can expose you to wood dust, a substance known to the State of California to cause cancer. Avoid inhaling wood dust or use a dust mask or other safeguards for personal protection. For more information go to www.P65Warnings.ca.gov/wood