When we're in a hurry or traveling light, we often resort to one-size-fits-most tools like adjustable wrenches and pliers. These tools are fine for rough work but are a poor choice when working on vehicles, machinery, and other precision equipment.

It's not that they can't do the job; it's that they frequently damage nuts and bolts—pliers because they have serrated jaws and adjustable wrenches due to an imperfect fit caused by slop in the mechanism.

Enter the German-made Knipex Pliers Wrench, a smooth-jaw adjustable plier with a unique gear-operated mechanism that keeps the jaws perfectly parallel to each other as they adjust to fit different size nuts and bolts. They perform the function of an adjustable wrench but with a better fit because they grasp tight like pliers.

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The trick to their design is the operation of the lower jaw; instead of pivoting on a pin, it slides up and down on a pair of grooves. It does this in response to the motion of the upper handle, which engages by means of a cam-like projection that fits into a matching indentation on the back of the jaw.

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Gross adjustments are made by pressing a spring-loaded pin and engaging with different sets of teeth in the serrated slot through one of the handles. The sliding jaw has between 1/4 and 3/8 inches of throw—meaning the jaws move that distance when the handles are squeezed or released.

It's an ingenious configuration that allows for quick adjustment and a tight fit to nuts, bolts, and whatever else is held in the jaws. According to Knipex, the Pliers Wrench offers a 10:1 mechanical advantage, so if your grip is strong you can use it to loosen very tight bolts.

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They can be made to mimic the action of a ratcheting wrench by releasing tension on the "back stroke", a handy feature when working in tight quarters, where it would be necessary to remove and reset an adjustable wrench.

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You might think it would be possible to provide similar functionality by putting smooth jaws on conventional pliers, but you can't. When you rely on a pivot, there's only one position at any given opening size where the jaws are parallel—which is what you want from a wrench. The jaws of the Pliers Wrench are always parallel.

The Pliers Wrench has been available in Europe for more than a decade. I first saw them several years back and was so entranced by their operation that I immediately ordered the 7-inch model. This was at a time when Knipex had minimal U.S. distribution; their tools are now much easier to get.

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I wasn't sure how much I would use these pliers, but now that I have them they're my go-to tool for applications where I would otherwise use an adjustable wrench. I recently bought the 10-inch model, though I do not use it quite as much as the smaller size. The tool is also available in 6-, 12-, and 16-inch models with dipped or ergonomic grips.

The Pliers Wrench is made in Germany, so it isn't cheap, but as with so many tools it is one where you get what you pay for.