The triangular (architect’s) scale is a drawing and measuring tool, about 30 cm long, with which one can draw and measure lines at different scales. It is an indispensable tool in architectural design. On each of the three faces there are two different scales, giving a total of six usable scales. Each edge is allocated to a particular scale or pair of scales (e.g. 1:2, 1:5, 1:10, 1:20, 1:25, 1:33, 1:50, 1:75, 1:100, 1:125, 1:150, 1:200, 1:250, 1:500 or 1:1000).

Triangular scales can be made of plastic or aluminium. If buying one you should ensure that it has as many possible different scales as possible. Of course, the scale 1:2 can be easily converted to use for drawings at a scale of 1:20 and 1:200 and so forth.

A triangular scale is placed on a scale design sketch in order to determine the scale, to check a particular dimension in the sketch, or to change a dimension. The triangular scale is also suitable for measuring existing plans or drawings that have no dimensions, but whose scale is known. If you draw freely without any existing basis you can draw the ­desired length in metres directly to the desired scale.

Rulers and set squares can be used to check rapidly made sketches to see whether their dimensions and proportions need to be developed further. Straight-edge rulers produce mono dimensional drawings. Their disadvantage is that they are suitable only for drawing straight lines. They are, however, ideal for constructing perspectives with one or more vanishing points. The transparent set square, which is also used for technical drawing, is very useful for drawing parallels and lines at right angles, or any other angle required, to a given line. The length of the ­hypotenuse (the long side of the triangle) should be 32 cm. A grip makes this implement easier to use.

French curves are available as prefabricated stencils. They come from the field of mathematics, where they are used to draw parabolas and functions. In architecture they are particularly useful for drawing round design elements, especially in perspective. If a particular curve is not available a flexible curve can be used. A circle template with circles of different diameters is always useful.