This is a very narrow way of reciprocating needles (zigzag). It may appear as a thin line on a sketch, either straight or curved. Because the cut edge after a narrow stitch is firm and firm, it is often used to wrap edges. Sometimes it is scallop with narrow needles, sometimes it plays a reinforcing role with the needle. It is safest to use narrow needles after scissors scissors. It also protects wider needles. The dots in the picture represent the stitches returned, which are not normally drawn.
When a narrow needle is tilted, fewer needles are needed, and it is commonly used in flower stems and other designs.