This is a very well made tool. I purchased 2 of them to seam some solid surface (Corian type) countertops and is used to pull the countertop sections together while the adhesive/glue sets. The suction cups are vacuumed sealed to the surface by pumping the piston on each suction cup. My advice, play with these a little before you actually use them in a gluing session.Ididn't and discovered that one of the suction cups wasn't working properly after I had applied the adhesive and had to scramble to get it working. I had tested one of them earlier, but not the other and almost had a failure at the critical time. After the adhesive had set, I repeatedly applied and released suction on the questionable suction cup and now it works fine. I guess in manufacturing or storage one of the piston pumps wasn't quite seated properly and the pump didn't pull a good vacuum. After working the unit several times it now works flawlessly. FYI, there is no mechanical release on the suction cups, you just lift an edge of the suction cup to release the suction.Lastly, make sure you know how to tighten the tool to apply pressure to the seams. I had a couple of friends over to help with the seaming process and they kept trying to turn the pressure applying knob in the wrong direction. Remember, righty tighty, lefty loosey to screw in or loosen a bolt. Except in this case, when you tighten (turn the knob right) you are actually pulling the suction cups apart. And when you loosen (turn the knob left) you are applying pressure against (fixed) the top rails to push the movable suction cup towards the other fixed suction cup. So, it's lefty loosey to tighten (apply pressure) to you seam joint. Just make sure you know which way to turn the knob before you are actually doing a seam job and they will work great.