Rip Saws are generally used for ripping solid lumber planks. They come in either single blade or multiple blade configurations. Some multiple blade machines have one or more movable blades to facilitate the cutting of variable widths. Some are controlled electronically. They are often used in a lumber defecting operation. Some single blade machines are called Straight Line Rip Saws, meaning that they are capable of cutting to tolerances acceptable for later lamination for solid wood furniture, etc... The more accurate machines have the timbers transported on a knurled feed chain to control the timber more precisely. Some, generally less precise, machines are roller fed. Rip saws are generally used in larger production furniture or moulding factories where wider planks are reduced in width for subsequent operations.