Fits on most sewing machines having a slide plate. Slip Wico Lifetime Thread Cutter onto plate and close. Its own spring tension will hold it in place. At completion of sewing, operator draws thread under lip of cutter and onto "V" slot. Thread is cut and secured under lip by spring tension, thus preventing needle from becoming unthreaded. Easily sharpened. One or two strokes of a stone gives it a "like new" cutting edge. Made of the best quality high carbon spring steel.