What are machine jigs? A jig is designed to guide a cutting tool and is normally used when manual operations like drilling or reaming are required. A fixture is a heavy-duty manufacturing aid used to secure and align raw materials in a CNC machine for example. What is a jig and fixture? Jigs and fixtures are manufacturing tools that are used to produce identical and interchangeable components. These workholding and tool guiding devices are designed for use in the machining and assembly of parts. What are jigs and fixtures for machine shops? Jigs are commonly used in drilling, boring, reaming and tapping, while fixtures are used for milling, slotting, shaping, turning and planning. Jigs are usually more expensive than fixtures. Jig designs are often more complex than simpler fixture designs.