A "Ringschlüssel," or ring spanner, is a type of hand tool used for tightening or loosening nuts and bolts. It features a closed loop at one end that fits over the fastener, providing a secure grip. This design allows for better torque application compared to open-end wrenches, making it ideal for working in tight spaces. Ringschlüssel come in various sizes to accommodate different fastener dimensions. They are often made from durable materials like steel to withstand high levels of force. Commonly used in automotive repair and construction, they are essential tools for mechanics and DIY enthusiasts alike.