The design of the seam size is theoretically greater than the thickness of the cloth belt. When considering this dimension, metal zipper it is important to prevent the insertion of the lamella in the fabric seam of the pull head, or the embedding of the lower cover plate of the pull head. The size of the seam is less than the thickness of the drawing and the thickness of the cover plate.When the chain tooth by importing, constantly pull your head into the body, pull the size of the head of the body cavity edge state slowly become smaller, thus promoting the chain tooth space into each other. Before entering the chain tooth, the teeth of the chain teeth should be opened first, like the mouth opening, then the other tooth will enter and finally contain. How about the mouth opening? Obviously, head mouth big teeth, tooth chain into easy to each other, but the mouth piece is too large, it may appear the other two tooth head into a chain between teeth at the same time, this creates a double teeth, obviously is not qualified, If the tooth of the tooth is too small, the other tooth is not easy to enter, the appearance of the teeth head touching the head, causing meshing difficulties.