A hot water bottle is a flexible container filled with hot water, used to provide warmth and comfort. Typically made from rubber or thermoplastic, it has a screw or stopper to prevent leaks. People often use hot water bottles to soothe aches, relieve menstrual cramps, or keep warm during cold weather. To use a hot water bottle, one fills it with hot (but not boiling) water, ensuring to leave some space for expansion. It can be placed under blankets or directly on the body. Hot water bottles are a simple, effective, and reusable solution for warmth and pain relief.