A hot water bottle is a flexible container, usually made of rubber or thermoplastic, designed to hold hot water. It is commonly used to provide warmth and comfort, especially during cold weather or to soothe aches and pains. The bottle is filled with hot water and sealed, allowing it to retain heat for several hours. Hot water bottles can be used in various ways, such as for warming beds, easing menstrual cramps, or relieving muscle tension. They are often covered with a soft fabric to enhance comfort and prevent burns. Many people find them a simple and effective remedy for discomfort.