Figure 2-25.-Setting up and bracing a ridgeboard when only a few workers are available.

Figure 2-25.-Setting up and bracing a ridgeboard when only a few workers are available. called collar ties (fig. 2-23). In a finished attic, the ties may also function as ceiling joists. To find the line length of a collar tie, divide the amount of drop of the tie in inches by the unit of rise of the common rafter. This will equal one-half the length of the tie in feet. Double the result for the actual length. The formula is as follows: Drop in inches times 2, divided by unit or rise, equals the length in feet. The length of the collar tie depends on whether the drop is measured to the top or bottom edge of the collar tie (fig. 2-23). The tie must fit the slope of the roof. To obtain this angle, use the framing square. Hold the unit of run and the unit of rise of the common rafter. Mark and cut on the unit of run side (fig. 2-24). METHODS OF RIDGE BOARD ASSEM- BLY.— Several different methods exist for setting up the ridgeboard and attaching the rafters to it. When only a few Builders are present, the most convenient procedure is to set the ridgeboard to its required height (total rise) and hold it in place with temporary vertical props (fig. 2-25). The rafters can then be nailed to the ridgeboard and the top wall plates. Plywood panels should be laid on top of the ceiling joists where the framing will take place. The panels provide safe and comfortable footing. They also provide a place to put tools and materials. Common rafter overhang can be laid out and cut before the rafters are set in place. However, many Builders prefer to cut the overhang after the rafters are fastened to the ridgeboard and wall plates. A line is snapped from one end of the building to the other, and the tail plumb line is marked with a sliding T-bevel, also called a bevel square. These procedures are shown in figure 2-26. The rafters are then cut with a circular saw. Figure 2-26.-Snapping a line and marking plumb cuts for a gable-end overhang. 2-17