A combination wrench is a hand tool used for tightening or loosening nuts and bolts. It features two ends: one with an open-end design for gripping flat sides of fasteners, and the other with a closed-end, or socket, that fits over the head of a bolt. This versatility makes it a popular choice in both professional and DIY settings. Combination wrenches come in various sizes, typically measured in either metric or imperial units. They are often made from durable materials like chrome vanadium or chrome molybdenum steel, ensuring strength and longevity. Many sets are available, allowing users to have a range of sizes for different tasks.