Topstitching is decorative stitching on garment edges. Used for both functional and decorative purposes. Generally done 1/8-1/4 inch from garment edge
Overlock stitches sew over cloth edges for edging, hemming, or seaming. Machines use loopers instead of bobbins for thread control. Runs at speeds from 1000 to 9000 rpm. Also known as serging, overedging, or merrowing
Lockstitch uses two threads that lock together in fabric. Upper thread runs through needle, lower thread through bobbin. Rotating hook catches upper thread around bobbin, forming lockstitch. Thread tension mechanisms prevent entwine point from leaving center
Sewing needle consists of shaft, groove, eye, scarf, and point. Modern needles are made from steel wire with nickel or gold plating. Needle size decreases in length and thickness