ing the length of the long side (hypothenuse) of a right
angle triangle, when the other two given sides are not equal, the foot
rule, or another steel square may be laid diagonally across the blade
and arm, and applied directly to the proper graduations thereon, and
the distance between them measured on the rule. If the distance to
be measured is in feet, use the 1/12" graduations on the back of the
square.

[Illustration: Fig. 194. Face of Steel Square, Octagon,
"Eight-Square," Scale.]

To use the octagonal (or 8-square) scale, Fig. 194, which is along the
center of the face of the tongue, with the dividers, take the number
of spaces in the scale to correspond with the number of inches the
piece of wood is square, and lay this distance off from the center
point, on each edge of the board. Connect the points thus obtained,
diagonally across the corners, and a nearly exact octagon will be had.
E.g., on a board 12" square, Fig. 195, find A.B.C.D., the centers
of each edge. Now with the dividers take 12 spaces from the 8-square
scale. Lay off this distance on each side as A' A" from A, B' B" from
B, etc. Now connect A" with B', B" with C', C" with D', D" with A',
and the octagon is obtained.

[Illustration: Fig. 195. Method of Using the Eight-Square Scale on the
Steel-Square.]

In making a square piece of timber octagonal, the same method is used
on the butt, sawed true. When the distance from one center is laid
off, the marking-gage may be set to the distance from the point thus
obtained to the corner of the timber, and the piece gaged from all
four corners both ways. Cutting off the outside arrises to the gaged
lines leaves an octagonal stick.

[Illustration: Fig. 196. Back of Steel Square, Essex Board Measure.]

The board-measure is stamped on the back of the blade of the square,
Fig. 196. The figure 12 on the outer edge of the blade is the starting
point for all calculations. It represents a 1" board, 12" wide, and
the smaller figures under it indicate the length of boards in feet.
Thus a board 12" wide, and 8' long measures 8 square feet and so on
down the column. To use it, for boards other than 12" wide:--find the
length of the board in feet, under the 12" marked on the outer edge of
the blade, then run right or left along that line to the width of
the board in inches. The number under the width in inches on the line
showing the length in feet, gives the board feet for lumber 1" thick.

For example, to meas