A carpenter pencil is a uniquely functional piece of equipment. You can recognize one because it is much larger and stronger than a regular pencil and has no eraser. It usually also has a hexagonal shape with flat sides.
Why Flat Sides?
In fact, the sides are not always flat on carpenter pencils--sometimes the pencil is more of an oval. In either case, the sides serve to keep it from rolling away, even when placed on an inclined surface.
Carpenter pencils typically have harder--and therefore stronger--graphite, and write well on most surfaces. They are used not only by carpenters but by masons and many other craftspeople as well. Many draftsmen also like the stronger, flat graphite that they can shape to their liking.
Pencils date to 16th century England, but the earliest known example of a carpenter pencil like the one used today was found in a German house in the 17th century.
Carpenter pencils won't fit in a regular pencil sharpener. Although there are specially designed handheld sharpeners available for the pencils, workers in the building trades usually use a knife to make a chisel end (for fine lines) or a flatter end for writing on textured material surfaces, such as brick.
Carpenter pencils can come in many sizes. Flat-sided pencils are popular in a 7/16-inch width, while elliptical pencils are popular in a 1/2-inch width.