Thin Tapered Jaws, Specially Designed to get into Narrow openings. Fully Hardened and Tempered Chrome Plated & Black Finished (Phosphated),Drop Forged carbon steel/chrome Vanadium Steel an adjustable wrench is a tool, which can be used to loosen or tighten a nut or bolt. It has a "jaw" (the part where the nut or bolt fits), which is of adjustable size .