Heat mat warms up the surface evenly. It only needs to be connected to a thermostat to rich the correct temperature. For the wellbeing of your animal never cover the whole surface of the terrarium with the heat mat but create a hot spot. Do not, in any case, overlay, fold, cut, drill or immerse the mat in water.
The heat mat comes with a 50°C safetystop to avoid any unwanted damage to the animals.