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 the
two shorter sides being 40 inches long must be the value
of x in the proportional equation 30.42.43::40:x, or
about 56.57 inches.
Notice that the last item in the brace table (the one
farthest to the right in fig. 2-11) gives you the
hypotenuse of a right triangle with the other proportions
18:24:30. These proportions are those of the most
common type of unequal-sided right triangle, with sides
in the proportions of 3:4:5.
The primary use of the Essex board measure table
is for estimating the board feet in lumber of known
dimensions. The inch graduations (fig. 2-12, view A)
above the table (1, 2, 3, 4, and so on) represent the width
in inches of the piece to be measured. The figures under
the 12-inch graduation (8, 9, 10, 11, 13, 14, and 15,
arranged in columns) represent lengths in feet. The
figure 12 itself represents a 12-foot length. The column
headed by the figure 12 is the starting point for all
To use the table, scan down the figure 12 column to
the figure that represents the length of the piece of
lumber in feet. Then go horizontally to the figure
directly below the inch mark that corresponds to the
width of the stock in inches. The figure you find will be
the number of board feet and twelfths of board feet in a