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出典:『Wikipedia』 (2011/05/02 14:46 UTC 版)

英語による解説

引用

The Rafter angle square is a triangular-shaped measuring tool used to draw straight lines on lumber to be cut, or to lay out angles for roofs, stairways, decks and other general construction. The tool is marked with degree gradations for fast layout and cutting of lumber without performing complex trigonometry calculations. It was invented in 1925 by Albert J. Swanson. He called it the "Speed Square," since it provides a short cut for measurements and calculations of angles.