putting a uth on the side of the tank is pretty much pointless, you want the gecko to get belly heat. Depending on the brand uth you get will depend on how you place it to the tank. zoo med mats come with adhesive on them already, but once you put it on the tank you cant remove it without damaging it. If you get a ultratherm or fulkers, you can use aluminum tape to apply it to the bottom of the tank, and can move the mat if you wish. You can use the pads meant for the bottom of chairs to prevent the chairs from scratching hard wood floors to raise the tank up so the uth has air flow.