They have a slot on the back of the actual thermometer to slid the end of a suction cup into it. I have both of my accuriate thermometers attched to the side of the glass about 3 inches above the substrate with suction cups I found at Michaels Craft store. I'm sure you could find suction cups anywhere though. They hold up to 4 pounds, so even when my baby girl decides to use one as a resting spot, they stay in place.

Hope that helps.

Also by using the suction cups, you avoid using any sticky substances in the enclosure, which could get dislodged and attached to the scales of your snake.