Hair Dryers work well too. I'll usually sit down in front of my rack with all of my thawed rats and start going over them with the hair driyer to heat them up. The positive to this is after a couple minutes with the hair dryer, the snakes have picked up on the scent of warm rat in the air, and they know its feed time. Most of my snakes are sitting at the front of their tubs drooling before I even feed the first rat out.