[ctroein89]

For carpentry, 12-inches-to-a-foot isn't actually that useful, since wood is never the nominal size. For lumber, nominal sizes are measured assuming that sawing and planing remove no wood, but sawing and planing will remove about 1/4 to 1/2 an inch in each direction. That means that you can't stack two 2x4 to get an exact 4x4, and you can't use dimensional lumber to fill a nominal 1 foot gap without cutting.

Carpentry, both the house-building and furniture making kinds, have adapted by emphasizing tricks to measure lumber without rulers. That means starting with more wood than needed, and cutting down to make pieces fit.