Actual Dimensions
The “Dumb” Definition: The collective fiction we all agree to live with where a 2x4 board actually measures 1.5 x 3.5 inches because the lumber yard stole the other half-inch and called it "surfacing."
The Job-Site Truth: The exact physical measurement of finished lumber after drying and planing. If an architect designs custom built-ins around "nominal" sizes without measuring the actual wood, someone is going to be crying on install day.