A mechanical vise is a tool used to securely hold objects in place while they are being worked on. It consists of two parallel jaws that can be adjusted to grip items of various sizes. Mechanical vises are commonly found in workshops and are essential for tasks like cutting, drilling, or sanding materials such as wood and metal. These vises can be operated manually using a screw mechanism or a lever, allowing for precise control over the clamping force. They are often mounted on workbenches for stability and can be made from materials like steel or cast iron for durability.