Fig. 1—Method of levelling the foundations for a concrete yard or floor 40ft. wide and with a slope of 1 in 20. Upper: Section through the first line of pegs. A—Edge of drain used in place of the first peg. B—Vertical fall, which is found by dividing the horizontal unit of the slope ratio (20) into the horizontal length of fall (40); that is 40/20 = 2ft. C—Second peg. Third peg. E—Intermediate pegs even with the line of sight between the edge of the drain (first peg) and the third peg. F—Level. G—Ground surface. Lower: Plan. A—Drain. B—Second peg. C—Third peg. D—Lines of pegs even along the line of sight between the back peg and- the drain edge and even along the line of sight from side to side. The back line of pegs may be level or sloped toward the third peg if required.

New Zealand Journal of Agriculture, Volume 80, Issue 2, 15 February 1950, Page 148

Fig. 1—Method of levelling the foundations for a concrete yard or floor 40ft. wide and with a slope of 1 in 20. Upper: Section through the first line of pegs. A — Edge of drain used in place of the first peg. B—Vertical fall, which is found by dividing the horizontal unit of the slope ratio (20) into the horizontal length of fall (40); that is 40/20 = 2ft. C—Second peg. Third peg. E— Intermediate pegs even with the line of sight between the edge of the drain (first peg) and the third peg. F —Level. G—Ground surface. Lower: Plan. A—Drain. B—Second peg. C—Third peg. D —Lines of pegs even along the line of sight between the back peg and- the drain edge and even along the line of sight from side to side. The back line of pegs may be level or sloped toward the third peg if required.