item is a nice idea but the base is plastic and cracks the first time I used it. there is a piece of metal under it but i don't see this item lasting very long in regular use. don't buy it, save your money.

I gave this product one star only because I couldn't select "zero" stars. The idea is not a bad idea, just poorly implemented. Despite reading several reviewers' reports that these clamps easily broke, I ordered them anyway since they looked like a solution to a common problem and I expected that the defect would have been fixed by now. Wrong! Without actually seeing the clamps, it may be hard to understand how they are made. There is a polycarbonate "base" with two "spring steel "clamps" attached via a separate polycarbonate "lid" which is screwed on. The lid is not strong enough to hold the clamps leading to stressing (bending) of the lid and potential failure. I did not actually use the clamps. One clamp looked "okay" in that the polycarbonate lid was not obviously stressed and deformed. The same was not true for the second clamp. I'm sure it would have failed the first time I used it. So, I returned the clamps to Amazon for credit which they did give. For awhile, I thought about remaking the polycarbonate lid out of something more substantial, thicker, or stronger, like aluminum. The lid is secured to the base via screws so this may have been possible. But, why should I have to do this, especially when I really would have to buy three more sets to use on any four sided box? At $10 per set, maybe I would have done this. But not at $25 per set! The manufacturing fix would have been at least to make the lid thicker. I usually read most of the reviews with a grain of salt and discount some where I think maybe the user was at fault. Here, I was at fault for not listening to other users. Conclusion: Good idea, bad design/manufacturing. It really should have been fixed by now.

I got these to help with holding material while I glued and nailed or screwed... The first one I got out of the package, broke within about 20 minutes. I dropped it off the work bench (I know I dropped it, but sometimes that happens) and the plastic casing that holds it together completely shattered. I like the concept of using it like a "third hand," but the product needs to be built better.

These clamps work great and make assembling cabinet panels so much easier. The spring clamps automatically hold your panels flush and has an index mark for interior panels and do not interfere with nail guns, etc. No more trying to balance plywood panels while looking for a bar clamps or drill. The clamps come in package of two (one left, one right). They also come with two plastic shims????? of whose purpose not specified in the package or directions. Since they are the same thickness as the clamp top, I believe they are a spacer to keep the panel level when resting on the clamp. I highly recommend this product.
[...]

UPDATE: Although very useful, I cannot highly recommend this product, due to its lack of durability. After only a few dozen cycles, on 3/4" plywood, the tops of the red clamps began to split either from material failure or lack of adequate reinforcement. I notified Jet Tools of the problem and they sent me a couple of new sets, to replace the broken ones. Hopefully they will redesign this product for long life. Once the problems are corrected I would highly recommend these clamps. In the interim, I will try to replace the broken plate with one made of plywood and see it the fault can be overcome. Pictures of the problem area are available in the Tool Review section of my Blog.

Broke on first use. When I received product I was pleasantly surprised at the size of the "clamps", They were more substantial in size than I had expected. I was building some drawers out of 5/8" stock and decided I'd see if the clamps would support the joints (just to see how they worked). The 1st attempt at attaching the the corner snapped the top plastic piece. I put the product back in the plastic case and call Amazon for a return. They promptly e-mailed me a RA# as well as supplied a prepaid return OK. Very disapointed with product, but at least pleased with Amazon.