BK is a fixed end for ball screw. It is commonly used in linear motion systems to provide a mounting point for the ball screw assembly on one end, while allowing the other end to move freely. The BK fixed end is designed to securely hold the ball screw in place and prevent any movement or rotation, ensuring accurate and precise positioning of the linear motion system. It is typically made of high-quality materials such as steel or aluminum to ensure durability and long-lasting performance.