A jointer is a woodworking tool used to create flat surfaces on lumber. It helps to straighten and smooth the edges of boards, making them easier to join together. By removing any warps or twists, a jointer ensures that the wood pieces fit snugly, which is essential for building furniture or cabinets. Jointers come in various sizes and types, including stationary models and portable versions. They typically feature a flat table and a rotating cutter head that shaves off thin layers of wood. Proper use of a jointer can significantly improve the quality of woodworking projects, making it a valuable tool for both professionals and hobbyists.