RULE FOLDING 6' ENGINEERS (FT, IN, 1/8, 1/16 & FT, 10th, 100th). This Keson brand ruler is an essential tool for carpenters, masons, plumbers and all types of tradesmen. Ideal for drawing straight lines without using a chalk line or mason line. Designed for engineering or other measurements that require tenths and feet. Also, it extends to a length of 6 feet.