rafter extending beyond the outer edge of the plate. Ameasure line (fig. 2-4, view B) is an imaginary referenceline laid out down the middle of the face of a rafter. If aportion of a roof is represented by a right triangle, themeasure line corresponds to the hypotenuse; the rise tothe altitude; and, the run to the base.A plumb line (fig. 2-4, view C) is any line that isvertical (plumb) when the rafter is in its proper position.A level line (fig. 2-4, view C) is any line that is horizontal(level) when the rafter is in its proper position.FRAMING SQUARELEARNING OBJECTIVE: Upon completingthis section, you should be able to describe andsolve roof framing problems using the framingsquare.The framing square is one of the most frequentlyused Builder tools. The problems it can solve are somany and varied that books have been written on thesquare alone. Only a few of the more common uses ofthe square can be presented here. For a more detaileddiscussion of the various uses of the framing square insolving construction problems, you are encouraged toobtain and study one of the many excellent books on thesquare.DESCRIPTIONThe framing square (fig. 2-5, view A) consists of awide, long member called the blade and a narrow, shortmember called the tongue. The blade and tongue forma right angle. The face of the square is the side one seeswhen the square is held with the blade in the left hand,the tongue in the right hand, and the heel pointed awayfrom the body. The manufacturer’s name is usuallystamped on the face. The blade is 24 inches long and 2inches wide. The tongue varies from 14 to 18 inches longand is 1 1/2 inches wide, measured from the outer corner,where the blade and the tongue meet. This corner iscalled the heel of the square.The outer and inner edges of the tongue and theblade, on both face and back, are graduated in inches.Note how inches are subdivided in the scale on the backof the square. In the scales on the face, the inch issubdivided in the regular units of carpenter’s measure(1/8 or 1/16 inch). On the back of the square, the outeredge of the blade and tongue is graduated in inches andtwelfths of inches. The inner edge of the tongue isgraduated in inches and tenths of inches. The inner edgeof the blade is graduated in inches and thirty-seconds ofFigure 2-5.—Framing square: A. Nomenclature; B. Problemsolving.inches on most squares. Common uses of the twelfthsscale on the back of the framing square will be describedlater. The tenths scale is not normally used in roofframing.SOLVING BASIC PROBLEMS WITH THEFRAMING SQUAREThe framing square is used most frequently to findthe length of the hypotenuse (longest side) of a righttriangle when the lengths of the other two sides areknown. This is the basic problem involved indetermining the length of a roof rafter, a brace, or anyother member that forms the hypotenuse of an actual orimaginary right triangle.Figure 2-5, view B, shows you how the framingsquare is used to determine the length of the hypotenuseof a right triangle with the other sides each 12 incheslong. Place a true straightedge on a board and set thesquare on the board so as to bring the 12-inch mark on2-4

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