DO NOT PLUG HEATER INTO MAINS AT THIS STAGE See Heater Instructions in box for more Operating and Installation details. Place the heater pad on the decking  near the foot end of the bed. DO NOT place over any joints in the decking. Extend temperature sensor cable from control in through corner slot. Extend cable from heater pad through corner slot and plug firmly into heater control. NOTE: Only the Safety Liner and the Water Mattress should sit on top of Heater. Click here to view waterbed heaters.