If an instrument is available it will be located over this stake and the front line A-C, [Fig. 4], located by laying it off at 90 degrees from the side line already located. If no instrument is available, the front line may be laid off at right angles to A-B by holding a framing square at their intersection. This angle should be verified by the 6-8-10 method. This consists in measuring from the intersection at A along one line a distance of 6 feet and sticking a pin in the line at that point; a pencil mark may be used when the cord is white. In a similar manner, measure off 8 feet along the other line and then measure the hypotenuse of the triangle so formed. It should measure 10 feet. If it does not, the front building line must be shifted until it does. (4) With these two lines located, the remaining two lines may be located by measurement from them, the nail of stake A giving the starting point. Before this is attempted, however, the batter boards should be placed. Batter boards are variously constructed. Those shown are common types. They should be placed free of the foundation proposed by at least 3 or 4 feet. (5) Test the squareness of the whole lay-out by measuring the diagonals A-D and B-C. If the building lay-out is square the diagonals should be equal. If they are not equal, shift the cords at C and D, retaining their parallelism, until the diagonals become equal. (6) Once the lay-out is correct, saw kerfs should be made in the batter boards where the cords are placed. These kerfs will permit the cords being removed and replaced without further measuring.
2. Grade Line.—A properly drawn set of plans will show both the present lay of the ground upon which the building is to be erected and the new grade line which is to be established after the building is completed. The most convenient method of determining old grade lines and of establishing new ones is by means of the transit, [Fig. 1], or the Y-level, Figs. [3] and [5], with the rod, [Fig. 2.] Both instruments operate upon the same principle in grade work. The telescope is set level and sights taken thru it to the target upon the rod. The reading of the target's position upon the rod compared with the height of the telescope above the base, usually the street walk, determines the difference in grade of that particular placing of the target.
Fig. 5. Taking Sights with Y-Level
To locate levels for the masonry, (1) set the instrument at some convenient place and level the dial. (2) Having determined the height of the instrument above some predetermined base, such as the street walk, swing the telescope about and, making allowance for the difference in level as shown by the drawings, place successively stakes at each corner of the building with the required level marked thereon. As a rule, the mason has his own Y-level and uses it freely as the wall is constructed, especially where levels are to be maintained as the layers of material are placed.
Fig. 6. Leveling with Straight-edge
In a similar manner the earth grade about the building may be located, stakes being driven into the ground at frequent intervals and the amount of "fill" or reduction indicated thereon. Grade levels are established usually only after the builders are thru, except that the mason will have the grade indicated for him where the wall above the grade is to be differently finished from that below.
Where no surveyor's level is at hand, the mason or carpenter will secure the levels by means of a straight-edge of some 14 feet in length. A common level is placed upon this plank as shown in [Fig. 6.] By successive levels with stakes driven to indicate the successive levelings, a grade may be carried quite a distance without very great variations.
