Figure 2-12.-Segment of Essex board measure table.being 30 inches long has a hypotenuse of 42.43 inches.The length of the hypotenuse of a right triangle with thetwo shorter sides being 40 inches long must be the valueof x in the proportional equation 30.42.43::40:x, orabout 56.57 inches.Notice that the last item in the brace table (the onefarthest to the right in fig. 2-11) gives you thehypotenuse of a right triangle with the other proportions18:24:30. These proportions are those of the mostcommon type of unequal-sided right triangle, with sidesin the proportions of 3:4:5.Essex BoardThe primary use of the Essex board measure tableis for estimating the board feet in lumber of knowndimensions. The inch graduations (fig. 2-12, view A)above the table (1, 2, 3, 4, and so on) represent the widthin inches of the piece to be measured. The figures underthe 12-inch graduation (8, 9, 10, 11, 13, 14, and 15,arranged in columns) represent lengths in feet. Thefigure 12 itself represents a 12-foot length. The columnheaded by the figure 12 is the starting point for allcalculations.To use the table, scan down the figure 12 column tothe figure that represents the length of the piece oflumber in feet. Then go horizontally to the figuredirectly below the inch mark that corresponds to thewidth of the stock in inches. The figure you find will bethe number of board feet and twelfths of board feet in a1-inch-thick board.2-9