This Bed Warmer goes under the sheet and mattress cover where it stays out of sight, clean and flat. The cozy warmth of the bed warmer rises to keep cold feet and legs warm and comfortable all night long. Place the bed warmer at the foot of the bed (crosswise) next to the mattress and under the bottom sheet. It will not become wrinkled or tangled with the feet or bedding.
You may want to turn the bed warmer on about 30 minutes prior to entering the bed because it heats slowly. Be sure to turn the bed warmer off in the morning. One year manufacturer warranty.