The other day I saw a plumber tighten a bolt with what looked like an adjustable wrench. But it seemed like he didn't need to take it off the bolt every time to turn it further. Rather, it looked like the wrench's jaws were non parallel, or perhaps they had some give to them.

It didn't look like it was a ratchet; it looked like the jaws were sliding around the bolt when going back the "wrong" way. And it seemed like the adjusting mechanism was like a crescent wrench's. It was only around 6 inches (15cm) long, give or take, if that helps.

I tried searching for it on the web but couldn't find it.

What is this tool's name?

  • Could it have been a small. what some call, a monkey wrench?
    – SteveSh
    Jul 6, 2022 at 16:01
  • @SteveSh I don't think it was. But thanks. A monkey wrench won't be able to go "back" while connected.
    – ispiro
    Jul 6, 2022 at 16:16
  • 3
    The ones I have can "go back". One part of the jaw sort of floats, and loosens its grip when going backwards.
    – SteveSh
    Jul 6, 2022 at 16:33
  • @SteveSh Thanks. That's probably similar, then, to what I saw.
    – ispiro
    Jul 6, 2022 at 16:38

7 Answers 7


What you saw was a pipe wrench.

enter image description here

You can see the obvious black upper jaw there, with the adjusting nut on the upper jaw.

Not so obvious: the black upper jaw has about 5 degrees of flex/play, rotating about the logo sticker more or less. This means that leaning into the tool causes the jaws to come together slightly, and going the other way (ratcheting the tool) causes the jaws to come apart slightly.

This is designed for pipe (and pipe fittings made to work with this wrench). They are generally round and do not have flats. The wrench relies on the object being round, and gouges into it. The material must tolerate that.

This type of wrench is not the right thing for other fasteners that provide a hex or other means to lock onto the fastener. A pipe wrench would gore up the hex or other head, possibly crack it, and in any case reflect very poor workmanship.

The concept doesn't translate very well to hex fasteners. If the jaw opens enough to slide past the hex on the backstroke, it will slide past the hex on the forward stroke too! Also for the tool to work, the jaw needs to "dig in" to the material to stop it from sliding.

JACK links an open-end wrench with a notch in one of the faces, so you only need to slide it off about 2mm to allow the hex to slip by. The problem is, when engaged, it only has about 2mm of purchase on the most critical corner of the hex. That works under ideal conditions and low torques, so it looks good in the advert. But if the hex is even a little beat up it won't seat... and if too much torque is used, the 2mm contact point will round over, and then you'll really be up the creek... you won't be able to use other tools either.

  • Thanks. Your explanation made it clear that that is in fact what I saw, except I'm pretty sure he had one where the adjusting was done like in a crescent wrench, as opposed to the normal pipe wrench. Though I can't seem to find anything like it on the web. Anyway, thanks for the clear explanation!
    – ispiro
    Jul 6, 2022 at 19:12
  • You're right about those "speed" wrenches not being used for higher torquing. That's what the other end is for. We used them a lot in the electric utility business, dead end conductor clamps, 10 bolts per clamp.
    – JACK
    Jul 6, 2022 at 19:19
  • @ispiro They make them in all sizes, and a variety of angles of the working heads, designed to get into close clearances. Jul 6, 2022 at 19:21
  • Wera 6004 Joker is a similar concept for hex nuts and they do work quite well. They are self adjusting in a certain range and aren't available past 19 mm, so their use is limited, but can be immensely useful for some works.
    – Arsenal
    Jul 7, 2022 at 14:02
  • 2
    Just to add, these wrenches are often used in pairs: one on the fastener, and the other on the pipe (or whatever the fastener is attaching to) and facing the opposite direction as the first one. The second wrench hold the pipe so it doesn't spin when the fastener starts to get really tight (like black iron pipe on gas lines).
    – Z4-tier
    Jul 7, 2022 at 23:59

Most likely these are self-adjusting wrenches. There are a lot of variations of these, but here's one example:

https://commons.wikimedia.org/wiki/File:Self-adjusting_wrench.jpg (https://commons.wikimedia.org/wiki/File:Self-adjusting_wrench.jpg)

A search on big-box-site-of-your-choice will come up with many different varieties, most of which work roughly the same way.


serrated adjustable wrench.

eg: https://nz.rs-online.com/web/p/wrenches/1849011 (google has decided I'm an EE and is giving me EE relevant results) enter image description here

Bhaco's patent on these will have expired recetly beause I first saw this 20 years ago. Now they are available from several different brands.


could be these Renovator wrenches I have a set and they work as you described


  • Love these! They appear to be a bit of a novelty, but really work well.
    – Tim
    Jul 7, 2022 at 13:23

They are sometimes called open end speed wrenches. The splined open end gives ratchet-like speed for fast removal and installation. I am not affiliated with this company in any way.

enter image description here

  • Thanks. That's not what they were using since they were using an adjustable one, but it does look useful.
    – ispiro
    Jul 6, 2022 at 16:17
  • 2
    "Handles both metric and SAE", but doesn't handle either all that well. Seriously? One wrench for both? I can see the little notch in the open end for the different size head, but I wouldn't put much faith in that, especially if the nut you were trying to remove was stuck. Looks more like those are "Universal Bolt Rounders". I've become quite a fan of HF tools of late, but I'll be avoiding these.
    – FreeMan
    Jul 6, 2022 at 16:17
  • 1
    @FreeMan Seriously? One wrench for both? - Since they're not supposed to be precise (since that's what lets them move around), it might not be as bad as it seems.
    – ispiro
    Jul 6, 2022 at 16:21
  • Maybe so, @ispiro, but spending most of my time working on crusty, rusty bolts under the hood, I'd shy away from anything that doesn't give me a really good grip. I realize that's not what you asked, for, though, so maybe these will work well for you.
    – FreeMan
    Jul 6, 2022 at 16:44
  • 1
    @FreeMan Point taken. Thanks.
    – ispiro
    Jul 6, 2022 at 16:50

Sounds like a “c” wrench or spanner or plumbing spanner that has the top or finger hinged.

They don’t sound good but since most plumbing fittings do not need to be tightened to high torque settings then they work well.

They also work well in constricted spaces and even are designed so that they can get up to the nuts on the taps used in sinks which can be difficult to get to.

As I have many quality spanners I have been known to use them on plumbing fittings and they work fine, but given the restricted access it is not often they are any use. So the plumbing spanner gets used.

This is one version, there are others: enter link description here

This is similar to mine:

enter link description here

  • This doesn't look like what they were using, but it does look useful, so thanks!
    – ispiro
    Jul 6, 2022 at 16:18

Could be Robo Grip Pliers although they don't adjust like a crescent wrench. They're spring loaded so when you don't squeeze them they open up so you can move them easily.enter image description here

  • I have a pair of these - looks almost exactly the same actually. They're good when the thing you're turning is made of really hard metal, but they'll really eat up softer materials. Jul 8, 2022 at 17:59
  • 2
    I bought a pair of those 15-20 years ago. They came with some little form-fitted rubber sleeves that slipped over each jaw to protect whatever you were wrenching. They're kind of weak and almost useless compared to your general collection of typical garage wrenches. However, every few years when I think about throwing them away, a situation comes up where these are the ONLY things that work. Jul 9, 2022 at 0:01

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