① The installation of the piercing needle is too low, the bookmark does not penetrate or the penetration is not enough, which causes the piercing needle to fall down, and the thread roll when the claw is hooked is blocked by the book, resulting in small or no thread roll, which causes the thread to fall off, and the installation of the bottom needle should be improved. In addition, the incorrect pinholes of the bottom needle, the threading needle and the crochet needle are easy to fall off for the above reasons.

② The distance between the hook claw and the height of the threading needle should be adjusted according to the following figure to prevent disconnection. All threading needles and crochet needles must be on the same parallel line. The installation of crochet needles should be 5mm longer than that of threading needles. All bottom needles must be on the same parallel line. The height of the needle tip is the same. The rising point of the bottom needle can make the pinhole of the bookmark penetrate. All crochet claws must be on the same parallel line. The working position height of crochet claws and threading needles is generally 8mm, the hook claw tips are 0.2mm apart at the concave stop of the threading needle hole, and the hook thread is about 3mm to the right of the hook needle, protruding outward to ensure that the hook needle hooks the thread smoothly. After the hook thread, the hook needle is cropped. The threading needle rises with the lifting frame, and the hook claw returns to its original position from right to left.

③ hook wire claw and hook wire height installation is not reasonable, or hook wire hook wire when hook wire claw protruding degree is not enough, hook wire needle hook is not on the line and off the line, should make reasonable adjustment, but must pay attention to hook wire claw in the adjustment can not protrude too much, otherwise it is easy to cause hook double strands and off the line.

④ When the crochet needle rises or falls, it should rotate at an angle of about 180 degrees. The unreasonable rotation angle will also cause the thread to fall off. The crochet notch of the crochet needle should be turned to the front position when rising back, and the crochet should be turned inward to the left when falling.