A "computer numerical control" machine, (commonly called a "CNC" machine) is used to cut out shapes from sheets of plywood, OSB, or partical board for furniture and construction. To cut a rectangular hole, the computer must be programmed to make four straight cuts that meet at right angles. Each cut is defined by a point-slope equation and a length. The point-slope equation tells the computer at what point on the cutting grid it should start (the point), and at which angle it should go (the slope). Then the length tells it how far it should cut.
One cut is defined in the computer system by the line y-8=\frac{2}{7}(x-14) and a length of 100 units. A second cut, perpendicular to the first, starts at the same point and continues for 140 units of length.