2. The classification of sewing needles is as follows: According to the shape of sewing needles, they are divided into straight needles and curved needles. According to the shape of the needle tip, it can be divided into round needle and triangular needle. Circular needles are divided into 1/2 and 1/3 radians according to radians, and those with large radians are mostly used in deep tissues. The front half of the triangular needle is triangular and sharp, and it is used to sew tough tissues such as skin, cartilage and ligament, which is quite lethal. Therefore, except for the above tissues, round needles are used. In addition, when sewing with curved needle, the direction of force should be consistent with the arc direction of curved needle, and the needle should be pulled out from the tissue along the arc of curved needle when pulling out, otherwise it will be easily broken. According to the shape of the needle tail, it can be divided into eye type, split type and embedded type. Generally, there are many sewing needles for threading, but the split sewing needles that press the thread from the end of the needle are often easy to tear and break the thread, so they are used less. Because the needle tail is thick and the damage is relatively large, the so-called non-invasive needle (mosaic) can be used for some fragile and delicate tissues, such as blood vessels, nerves, intestinal walls and so on. That is, the needle with suture at the end of the hour hand can be made.