Play instruments to evaluate their sound quality and to locate any defects. Adjust string tensions to tune instruments, using hand tools and electronic tuning devices. Disassemble instruments and parts for repair and adjustment. Inspect instruments to locate defects, and to determine their value or the level of restoration required. Repair cracks in wood or metal instruments, using pinning wire, lathes, fillers, clamps, or soldering irons. Reassemble instruments following repair, using hand tools and power tools and glue, hair, yarn, resin, or clamps, and lubricate instruments as necessary. Compare instrument pitches with tuning tool pitches in order to tune instruments. String instruments, and adjust trusses and bridges of instruments to obtain specified string tensions and heights. Repair or replace musical instrument parts and components, such as strings, bridges, felts, and keys, using hand and power tools. Polish instruments, using rags and polishing compounds, buffing wheels, or burnishing tools. Shape old parts and replacement parts to improve tone or intonation, using hand tools, lathes, or soldering irons. Make wood replacement parts, using woodworking machines and hand tools. Mix and measure glue that will be used for instrument repair.