A partial sew-in is a form of weave or hair extensions. The first known hair extensions date back as far as ancient Egypt. The method of weaving hair that involves sewing was reportedly invented and patented by Christina Jenkins in 1951 (although there is some debate about this because ancient Egyptians were also rumored to have sewn in their hair extensions). Prior to the popularizing of sew-in weaves, hair was attached to the scalp with hair pins.
A half, or partial sew-in is a sew-in weave that only covers part of a person's head, as opposed to a full sew in that covers the entire head. Typically, with a half sew-in, the back and sides of the head are cornrowed down and tracks are installed, as with a normal weave. However, with a partial sew-in, the hair at the crown of the head is left out and styled to blend in with the hair extensions.