Brief characteristics of the processed material and its main physical and mechanical properties are given. The designs of machines and tools are considered, rational methods of work are shown. Safety measures are outlined. Longitudinal milling four-sided machines are designed, as the name implies, to mill the workpiece along the fibers simultaneously from four sides. Processing is carried out in one pass, which gives the machine undeniable advantages over single-spindle milling machines, especially in production lines for the production of multilayer window beams, floorboards and a variety of chasing products (platband, baseboard, staple, wagon, etc.).