The squaring shear performs three distinctly different  operations: When cutting to a line, place the sheet on the bed of the shears  in front of the cutting blade with the cutting line even with  the cutting edge of the bed. To cut the sheet with a foot shear,  step on the treadle while holding the sheet securely in place.  Squaring requires several steps. First, one end of the sheet  is squared with an edge (the squaring fence is usually used  on the edge). Then, the remaining edges are squared by  holding one squared end of the sheet against the squaring  fence and making the cut, one edge at a time, until all edges  have been squared. When several pieces must be cut to the same dimensions, use  the backstop, located on the back of the cutting edge on most  squaring shears. The supporting rods are graduated in fractions  of an inch and the gauge bar may be set at any point on the rods.  Set the gauge bar the desired distance from the cutting blade  of the shears and push each piece to be cut against the gauge  bar. All the pieces can then be cut to the same dimensions  without measuring and marking each one separately. Foot-operated shears have a maximum metal cutting capacity  of 0.063 inch of aluminum alloy. Use powered squaring  shears for cutting thicker metals.  [Figure 4-24] Airframe technicians use the throatless shear to cut aluminum  sheets up to 0.063 inches. This shear takes its name from the  fact that metal can be freely moved around the cutting blade  during cutting because the shear lacks a “throat” down which  Figure 4-25.  Throatless shears. Figure 4-26.  Scroll shears.  Figure 4-24.  Foot-operated squaring shear.  Scroll Shears Throatless Shear  1.  Cutting to a line 2. Squaring 3.  Multiple cutting to a specific size 4-10 Scroll shears are used for cutting irregular lines on the  inside of a sheet without cutting through to the edge.  [Figure 4-26]  The upper cutting blade is stationary while  the lower blade is movable. A handle connected to the lower  blade operates the machine. A hand lever operates the cutting blade which is the top blade.  Throatless shears made by the Beverly Shear Manufacturing  Corporation, called Beverly$^{TM}$ shears, are often used. metal must be fed.  [Figure 4-25]  This feature allows great  flexibility in what shapes can be cut because the metal can  be turned to any angle for straight, curved, and irregular cuts.  Also, a sheet of any length can be cut. 