I came across these Alden wrenches. They come in sets of 3 or 8, either metric or SAE from what I've seen. They are made of solid hardened stainless which I kinda like. The head has 2 pieces joined by a pin through the outer top jaw that passes through a slot of the inner jaw and main beam of the wrench. I drew lines 30' apart to illustrate the action.
Starting at the top and pulling down a full 60' you see the jaws as they fit the bolt the best.
At the bottom of the arc.
Now when you push up on the wrench the large jaw that is the larger top section of the jaw slides back toward the back of the wrench. You can see the top of the pin at the back along the wrench handle. There is a slot in the handle this top jaw and it's pin slide back and forth in. There is also a contour fit with the lower jaw which also guides and supports this moving top jaw.
Remember, the lower jaw is part of the main wrench handle and doesn't move as you push upward. When you have pushed up 30' a second set of contacts will grab the bolt and you can pull down again to turn the bolt but this doesn't feel as solid a grip on the bolt as when you push up 60'. You should push the wrench further upward to the 60' position to engage the other contact points which seem to grip the bolt much better. At this position you are back to the 1st photo and ready to start again.
Here is a picture in the secondary 30' position which will works but just doesn't seem as solid a grip as what you see in the 1st 2 photos.
This next shot shows the wrench sandwiched between a regular snap-on wrench and a snap-on line wrench all of the same 9/16 size. You can see that the Alden is i/2 way as thick as the line wrench across it's jaws.
So this ratcheting open ender has a secondary 30' position that will pull on a fastener a lot more than you could do with your fingers but it looks like it would slip at some point after too much pressure was on it. The 60' position looks pretty good. I've put about 20 ft lbs on the wrench in the 30' position and dam did I skin my knuckles when it let go. ....Naw, sorry, joking here, it didn't let go and it felt pretty solid actually. I put about 25 ft lbs on it in the 60' position and it felt pretty comfortable and solid as well. I think you could bust a lot of fasteners loose with it but for real stubborn ones use a regular wrench. It would be good along side line wrenches where you don't want to keep re-gripping the fastener. With the wide jaw pattern it should be pretty easy on fittings. I'll try to put these to work some more to get more experience with them. They are made in the USA and carry a lifetime warranty.
http://www.amazon.com/dp/B002W2HCGO/?tag=atomicindus08-20
http://www.chicagobrand.com/Alden.htm
and dammed if I didn't uncover another thread about this type wrench:
http://www.garagejournal.com/forum/showthread.php?t=133004