Surface planers, also known as planers, are woodworking machines that are primarily used for straightening wood that may be bowed, cupped, or twisted. The wood is passed over the top of the cutter block, and the fence is used as a reference to produce two straight faces at 90 degrees. This creates a flat and uniform surface for further processing. Depending on the intended use of the wood, it may then be passed through a thicknesser to produce accurately dimensioned timber. By combining these two operations, planer thicknessers can provide an efficient solution for both straightening and thicknessing wood.