One man can pour about 33 eight-inch joints, and two men can complete about 26 twelve-inch joints per hour on the bank where conditions are more or less fixed. =182. Labor and Progress.=—The labor required for the laying of pipe sewers, exclusive of excavation, bracing and backfilling, consists of pipe layers and helpers. For pipes 24 to 27 inches in diameter or smaller one pipe layer and one or more helpers are necessary, dependent on the size of the pipe and the depth of the trench. For larger pipes two pipe layers can work economically each working on one-half of the pipe and making half of the joint. The speed of pipe laying is ordinarily limited by the speed of the excavation, but on a job in Topeka, Kan.,[100] where the average day’s progress with a machine excavator was 200 to 500 feet of trench per day, the pace was limited by the speed of the pipe laying gang. This gang consisted of two pipe layers in the trench and two helpers on the surface. The sizes of pipes handled were from 8 to 27 inches. BRICK AND BLOCK SEWERS =183. The Invert.=—In good firm ground the excavation is cut to the shape of the sewer and the bricks are laid directly on the ground, being embedded in a thick layer of mortar. After the foundation has been prepared and before the bricks are laid, two wooden templates, called profiles, are prepared, similar to that shown in Fig. 126, to conform to the shape of the inside and outside of the sewer. Each course of bricks is represented by a row of nails in the profile and each nail corresponds to a joint in the row. The two profiles are set true to line and grade. A cord is stretched tightly between the two lowest nails on opposite templates and a row of bricks is laid. The bricks are laid radially and on edge with their long dimension parallel to the axis of the sewer and with one edge just touching the string. As each one or two or three rows are completed the guide line is moved up to the next nails. When the bricks are laid on the ground all but large depressions are filled in with tamped sand or mortar by the masons. Approximately the same number of rows of bricks is kept completed on either side of the center line. The succeeding courses follow within three to five rows of each other, the only bond between courses being the mortar joint. This is called row lock bond and with few exceptions has been used on all brick sewers in the United States. As the sides of the sewer become higher during the construction, platforms must be built for the masons. These platforms are built of wood and rest directly on the green brickwork. They should be designed to spread the load as much as possible. The brickwork of the invert is continued up in this way to the springing line. As soon as one section is completed one profile is moved 10 to 20 feet ahead along the trench according to the standard length of sections, and set in position. The line is then strung from it to nails