Measuring and marking-out tools for wood
Before making an item, the blank is marked out: the limits of work are drawn as lines. Carpentry uses a scale ruler, try square, mitre square, marking gauge, folding rule and tape measure. A try square draws right-angle lines and checks angles; a mitre square makes lines at 45°; a marking gauge draws lines parallel to an edge. First a flat side of the blank, the datum face, is chosen and all sizes are taken from it. The layer of wood removed during working is called the allowance; counting it saves wood. To draw a straight line, 2–3 points are marked from the datum face, the ruler is laid on them, held with the left hand, and the line is drawn with a pencil. 1 metre equals 100 centimetres.
Marking exercise: on paper and on a 4 cm × 20 cm strip (soft balsa wood or card): choose the datum edge, mark cut lines at 5, 10 and 15 cm with pencil and ruler and check the right angle with a try square. No sawing, only marking.