Copyright Goodheart-Willcox Co., Inc. 228 Section 4 Techniques After the excavation is performed, a drop line and plumb bob will be attached to locations where inter- secting lines create corners. Drop line is a mason’s line attached to a plumb bob to transfer line intersections down into the excavation to locate footings and walls. The drop line and plumb bob aid in determining the locations of footing and walls when preparing to install forms. Masons and other workers can refer to the lines created by the batter boards whenever they need to locate the different corners or face of the building. 12.2.3 Laying Out Wall Lines by Using 3-4-5 Method The following information identifies procedures to follow when laying out building lines using the 3-4-5 method. For more information on the 3-4-5 method, refer to Chapter 6, Math for Masonry Careers. Prepare the site where brick leads will be built. Deter- mine and mark the first wall corner location on the surface. Measure the length and mark the second out- side corner position. Hold the end of a chalk box line at one corner location, Figure 12-15. Extend the chalk box past the second corner positon and hold the line against the concrete. Raise the chalk line and snap it to mark the future brick wall location. See Figure 12-16. Recheck the length of the first wall and remark if needed. Use the 3-4-5 method to identify the first leg of the triangle. Measure 3′ from the corner and mark the location on the chalk line. To determine the second leg of the triangle, lay two tape measures on the chalk line. See Figure 12-17. All measurements will be performed from the inside edges of the tape measures. Hold the 5. If the dimension readings are the same, the building is square. If not, adjust the back corner lines on the batter boards, moving the lines the same amount in the same direction. Then recheck lengths of mason’s lines that represent walls to ensure they are accurate compared to the blueprint. 6. Remeasure diagonally and compare dimensions to determine if they are the same. Continue these procedures until the walls are appropriate lengths and diagonal dimensions are the same. 7. Once squareness is achieved, mark locations with nails or saw kerfs to permanently register them on the batter boards. Trade Tip The building layout must be square and not a parallelogram. A parallelogram is a shape similar to a square or rectangle but the corners are not at 90° to each other. Author’s image taken at Job Corps, Denison, IA Figure 12-15. Hold the end of a chalk box line at one corner location. Author’s image taken at Job Corps, Denison, IA Figure 12-16. Extend the chalk box past the second corner positon and hold the line against the concrete. Raise the chalk line and snap it to mark the future brick wall location. Author’s image taken at Job Corps, Denison, IA Figure 12-17. To determine the second leg of the triangle, lay two tape measures on the chalk line. All measurements will be performed from the inside edges of the tape measures. P R O C E D U R E (continued)