This section is from the book "Building Construction", by R. Scott Burn. Also available from Amazon: Building Construction.

**Scales Used In Drawings**. The scale to which drawings are constructed are conventional arrangements by which the proportion is maintained between the measurement which the drawing gives, and the actual length of the same parts when constructed, should be. Thus, a part of any building 15 feet in length could obviously not be drawn full size on paper; but if the length of each actual foot was supposed to be represented by a distance of an inch, a piece of paper a little over 15 inches in length would allow the line to be drawn; with a margin over, the line on the drawing paper would be 15 inches in length; but if the conventional measurement adopted was named in the drawing, it would be known that the line would be representing a line which in actual practice would be 15 feet in length. The formation of scales, of which the above is the general principle, is a matter comparatively simple, and will be found further illustrated in fig. 1, Plate 'XXXVIlla. Thus, suppose it is desired to construct a scale of " 2 inches to the foot," take in the compasses from a " foot-rule " the distance or extent of two inches, then draw any line, as a b, fig. 1, Plate XXXVIIIa., and from any point c, which will be the " zero " or " 0 " point of the scale, set off the distance in the compasses any number of times as there are to be feet in the scale, from c towards b, on the line a b, to d and c. The size of the Plate here limits the number of times the distance c d and b twice to three. Then each of the distances will represent a " foot." But as there are inches in the foot to be arranged for in the scale, divisions must be made to represent these inches; the large division to the left hand, as from the zero point, c to d, is that usually allotted to the inch division, this being divided, in large scales, into twelve equal parts, each representing an inch; but if the scale be small, as in fig. 10, then these first divisions, as a 6, fig. 3, Plate XXXVIIIa., is only divided into four parts, as a f, f e, d e, e b, each of these representing three inches, the extent or length of an inch in these small scales being guessed at. This is exemplified in the scale in fig. 10, which is a scale of " ¼ inch to the foot," or of " 4 feet to the inch." Fig. 8 is a scale of " 2 feet to the inch," or, as more commonly expressed, a scale of " ½ inch to the foot." Fig. 9 is a scale of "3 feet to the inch." Fig. 11 is a scale for a detail drawing, "one-fourth full size" or ¼ of a foot, or " 3 inches to the foot." Fig. 14 is a scale of 2/3 of a foot; or two-thirds of full size. Fig. 15, a scale of ⅝ of a foot or of full size, both with " eighths " marked. Fig. 4 shows the scale of 2 inches to the foot completed, with the division in the first division to the left indicating inches, all the larger divisions being feet. Fig. 2 represents a scale of " 1 yard to the 2 inches," the last division, a b, being divided into three, as a d, d e, and e b, each division representing a foot, the other divisions, as b f, representing a yard. Fig. 7 represents a scale of 10 feet to f of an inch, used like the last in laying down drawings of general plans, where the distances and measurements are great. In this scale of tenths, the last division is divided into ten equal parts, each representing a foot, and each of the larger divisions represent ten feet. Fig. 12 is a scale of " 5 feet to the inch;" and fig. 13, " 10 feet to the inch," with " inches " marked. Fig. 5 is a scale of " 1½ inches to the foot; " fig. 6, a scale of " 1 inch to the foot."

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