Machine weft is the most traditional extension method, one in which extensions can be attached by sewing or gluing. Sections of differing length can be used, with the approach depending on whether the goal is to add volume, highlights, or length. The technique also lends itself to clip-in attachment. 

In the sewn-in attachment technique, the natural hair is woven into a plait against the scalp, starting at the side and ending at the back of the head. Then, extensions are sewn into this plait, by means of the thread in the extension strip.