Instead of the nail used in methods 1 and 2, use a board about 8 to 12 inches long and of a width equal to considerably more than half of shaft _B_'s diameter. By nailing this board _x_ to the measuring rod _c_ at any suitable angle, you will be enabled to reach from the end _a_ well into the shaft _B_, as at _b_, and from _b′_ well into _A_, as _a′_. By keeping the board _x_ along its entire length in full contact with the shaft _B_ at both 1 and 2, the angular position of rod _C_ is bound to be the same in both instances, and you will thus (by the use of a square, as in Fig. 31) be enabled to aline _A_ parallel with _B_.
In all instances of parallel adjustment here cited it is assumed that both the alined and the alined-to shafts have been, as to secure accuracy of result they must be, properly leveled before starting to aline.
The above methods apply to cases where the shafting is already in place. Where, however, shafting is being newly installed before the work can be proceeded with, it is necessary, after determining on the location for the shafting, to get a line on the ceiling in parallel with the driving shaft to which to work to. Mark that point _A_ which you intend to be the center line for the proposed shafting upon the ceiling (Fig. 34).
Rest your measuring rod upon the driving shaft and at right angles to it, with the nail against it. Hold your square with the stock below and the tongue against the side of the measuring stick, so that its tongue extremity touches the ceiling mark _A_, and then mark a line on the rod along the tongue side _A_. Move your rod along the driving shaft to the point where the other end of the proposed shafting line is to be, and, squaring your stick to the driving shaft with the tongue side _A_ on the marked line of the stick, mark your section point on the ceiling. Draw a line or stretch a string between these points, and you have a true parallel to work to.
Owing to the supporting timber _B_'s interference, a square had to be used; but where the ceiling is clear the rod can be cut to proper length or the nail be so located as to allow of using the stick extremity _C_ for a marking point.
When a pulley is handily situated on the driving shaft, the method shown in Fig. 35 can be used to advantage.