Short definition
An adjustable wrench is a smooth-jaw wrench whose movable jaw is set by a knurled worm screw. It turns hex nuts and supply-stop nuts without leaving tooth marks on chrome, which is why it lives on every plumber’s belt. An 8-inch model handles most under-sink work; 10- and 12-inch sizes cover larger nuts.
What it is
The adjustable wrench has two jaws on a single head: one fixed, one driven by a small worm gear in the handle. Spin the worm to size the opening, then turn the wrench like any open-end wrench. Because the jaws are smooth, the tool grips by friction instead of bite, so it does not gouge soft brass, plated steel, or chrome.
“Crescent” is genericized from Crescent Tool Company (1907), the way “Kleenex” stands in for tissues. Plumbers usually own a few sizes — a 6- or 8-inch for tight work, a 10- or 12-inch for hose bibs, supply stops, and trap nuts. Quality matters here. Cheap adjustables develop slop in the worm and jaw within a year; a Channellock, Crescent, or Knipex Pliers Wrench will outlast the user.
Why it matters to a homeowner
The adjustable wrench is the right tool for any nut you do not want to scar. Chromed compression nuts on faucet supply lines, polished P-trap slip nuts, hose-bibb packing nuts, and angle-stop bodies all show toothmarks for life if you reach for a pipe wrench. The opposite is also true: an adjustable will round off a stuck threaded steel nipple where a pipe wrench would have bitten in. Knowing which jaw type to grab saves trips to the hardware store and avoids the small, embarrassing damage that turns a Saturday repair into a fixture replacement.
Common variants and not the same as
- Adjustable wrench vs. pipe wrench. Pipe wrenches have hardened toothed jaws and are designed to bite. Use them on raw threaded steel, never on chrome.
- Adjustable wrench vs. channel-lock pliers. Channel-locks reset on every grip; an adjustable holds its setting. Reach for an adjustable when you’ll turn the same nut size repeatedly.
- Adjustable wrench vs. basin wrench. A basin wrench’s pivoting head reaches faucet mounting nuts an adjustable cannot. They are not interchangeable.
Common failure modes
- Frozen worm screw. Stored damp, the worm corrodes and won’t turn. Soak in penetrating oil, brush, regrease.
- Loose jaw. Cheap wrenches develop play between the jaws. Once they round a nut, replace.
- Wrong size. Forcing a too-large opening down with finger pressure won’t hold. Size it tight before turning.