In the hand of the intelligent mechanic the square becomes a simple calculating machine of the most wonderful capacity, and by it they solve problems of the kinds continually arising in mechanical work. The blade of the square should be 24 inches long and two inches wide, and the tongue from 14 to 18 inches long and 1-½ inches wide. The tongue should be at right angles with the blade, or in other words the “square” should be perfectly square.