Figure 2-11.-Brace table.brace table, located on the back of the tongue; and theEssex board measure table, located on the back of theblade. Before you can use the unit length rafter table,you must be familiar with the different types of raftersand with the methods of framing them. The use of theunit length rafter table is described later in this chapter.The other two tables are discussed below.BraceThe brace table sets forth a series of equal runs andrises for every three-units interval from 24/24 to 60/60,together with the brace length, or length of thehypotenuse, for each given run and rise. The table canbe used to determine, by inspection, the length of thehypotenuse of a right triangle with the equal shortersides of any length given in the table. For example, inthe segment of the brace table shown in figure 2-11, youcan see that the length of the hypotenuse of a righttriangle with two sides 24 units long is 33.94 units; withtwo sides 27 units long, 38.18 units; two sides 30 unitslong, 42.43 units; and so on.By applying simple arithmetic, you can use thebrace table to determine the hypotenuse of a righttriangle with equal sides of practically any even-unitlength. Suppose you want to know the length of thehypotenuse of a right triangle with two sides 8 incheslong. The brace table shows that a right triangle with twosides 24 inches long has a hypotenuse of 33.94 inches.Since 8 amounts to 24/3, a right triangle with two shortersides each 8 inches long must have a hypotenuse of33.94 ÷3, or approximately 11.31 inches.Suppose you want to find the length of thehypotenuse of a right triangle with two sides 40 incheseach. The sides of similar triangles are proportional, andany right triangle with two equal sides is similar to anyother right triangle with two equal sides. The brace tableshows that a right triangle with the two shorter sides2-8

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