The first thing to consider when purchasing an electric blanket is choosing a heated over blanket or underblanket. Over blankets are heated electric blankets with controls placed over the sleeper at night. Underblankets are sometimes referred to as electric mattress pads, which are placed under the bottom sheet at night. For safety reasons, underblankets should never be used on top of the sleeper, and multiple underblankets or over blankets should never be used at the same time. In addition, when using over blankets, it is important not to sit on top of the blanket or pile pillows, blankets, toys or other items on top of it.