A jointer is a woodworking tool used to create flat surfaces on lumber. It helps to straighten edges and flatten boards, making them easier to join together for projects. Jointers come in various sizes, from small benchtop models to larger industrial machines, and they typically feature a long, flat table and a rotating cutter head. Using a jointer involves feeding the wood through the machine, which removes material from the surface. This process ensures that the edges of the wood are smooth and square, allowing for better connections with other pieces. Proper use of a jointer is essential for achieving high-quality woodworking results.