1. Flat seam: Trim the seam head of the upper piece or the lower piece, then sew it by lap seam method, then stick it with rubber agent, then sew it flat at 0.3cm away from the trimmed edge, and sew another line at 0.6cm.

2. Overlapping seam: sew a flat seam 0.3cm away from the trimming edge.

3. Mosaic seam: cut some seams neatly on both sides of the cut piece, cut a thong according to the length of the seam, the width of which is twice the sewing width plus 1.3cm, then put the thong between the two seams and add rubber agent, and finally sew the two sides. Note that the rubber agent is difficult to remove, so the rubber agent cannot stick to the seam line.

4. For the seams of collar, pocket and welt, cut off the seams of the two layers first. The edges of the two trimmed layers can be aligned from the reverse side of the leather, bonded with adhesive, and then stitched at a distance of 0.3cm, and finally stitched at a position 0.6cm away from the edge.

5. For thick leather, it can be treated by flat sewing, or it can be sewn by the following methods: before sewing, cut a small mouth with the length of 1.3cm on the overlapping layer on the inner side of leather according to the zipper mark, cut off 1.3cm on the top layer, and finally sew a circle along the trimming. The sewing of the outer zipper is to cut off both sides of the leather before sewing it on the clothes.