The tool named a square is a right angle, and consists of a steel tool whose broad side or surface is bounded by two right angles which are parallel to each other. We may say also that the simplest sort of right angle or square is that which is formed by bending a straightedge at one place only until the two arms extending from the bend are at right angles to each other; consequently, the straight-edge or parallelopiped is more like a square previous to being bent than it is afterwards; and at the present time a square may be termed a ninety, and other angular gauges may be named sixties, forty-fives, or some other number, to denote the quantity of degrees in their angles, until a circle's circumference shall be considered to have one hundred degrees, or some other number than three hundred and sixty. A square having its two arms of equal width and thickness is denoted by Fig. 287; such a square is said to have no back, or, properly speaking, no pedestal, and the tool is used for scribing right angles ; for this purpose it is laid with its broad side in contact with the work to be scribed, and held or fixed in position, and, while securely held, a scriber is moved along the edges of the square, and at the same time in contact with the work which is being scribed. A square having legs or arms of equal thickness is also sometimes used for adjusting pieces of work; when thus used, the square is preferred merely for its lightness and portability. The two squares shown by Figs. 287 and 288 are termed el-squares, through resembling a letter L; and the one denoted by Fig. 288 is also a pedestal square, because one of its arms is thicker than the other; and the thinner arm extending from the pedestal is the blade. The pedestal of a square is also its handle, being that which is held in the hand while applying the tool to a piece of work. A good pedestal-square is distinguished by means of a plane surface, which is placed in a horizontal position in some convenient situation for reference. On to this plane is put the square so that its pedestal shall rest on the surface and the blade extend upwards; and while thus resting the blade should be at right angles to the plane, whether viewed on the broad side, edge, or corners of the blade ; if not, the blade is bent, or some other defect exists in the tool and requires adjustment. Pedestal-squares are used for adjusting surfaces of a piece of work to a right angle with each other, also for fixing one piece of work at right angles to another piece, or to a table of a machine.