You have all seen the new generation of pliers that seem to have automatically adjusting jaws. What do they do, and do they really work?
If you look at how a pair of regular pliers grab a nut or bolt, you will see that the jaws are not parallel and hence do not grab both sides of the nut evenly. Hence using this kind of device will tend to round off the corners of the nut, making it difficult to grab with a proper wrench.
That is why the slip-lock and channel-lock pliers were invented some time ago, it allowed the jaws to be opened to a second width, or to several widths defined by the channels in the handle. These worked pretty well, although the two position slip-lock were still limited and tended to force the hand grip into an imperfect position.
The newest generation of self adjusting pliers are designed to open way up and then when they run into pressure while closing them, a ratchet device slips into position allowing for squeezing pressure at that opening. The wonderful thing about all of these pliers is that the jaws are parallel at all the possible positions, automatically parallel, and the handle is always at an opening for a good grip.
Of course the idea has been launched so you will now find this style of pliers in all kinds of formats, and in a wide variety of levels of quality. The technology is good. You have to pick your price according to the quality and durability that you need. The ones I had on the TV were from Stanley Tools.