Jointing

Jointing is the process of flattening a board's face or truing an edge perfectly straight and square, using a jointer machine or a hand plane worked carefully down the length. It's usually the very first milling step on rough lumber, because every later cut -- ripping to width, planing to thickness -- depends on starting from at least one flat, true reference surface. Skip jointing and every subsequent cut just repeats and compounds whatever's already wrong with the board.