I took a piece of scotch tape (the clear kind) and taped the probe inside the warm hide about halfway (*this idea was originally from Smulkin) so this way I know exactly what he is feeling in the hide as for the cold one I just set the guage on the floor next to the cool hide because the one I have measures one temp and humidity at the display. So I just prop it up against the back of the tank next to the cool hide. Basically you just want to get the probe as close to the substrate as possible so you can read what they are feeling. I am going to eventually get a suction cup so i can stick the unit to the back rather than propping it up because when Icculus goes cruising he takes it out. I didn't use the tape just because I didn't want marks on my tank later and I knew I would have to take it out to clean the tank walls.