Thread Repair Inserts, The Solid Alternative for Thread Repair. Designed to repair damaged threads or for use in original equipment, Keyserts® provide easy installation and versatility. Featuring a key-locking action that prevents rotation due to vibration or torsion, commercial-grade Keyserts can be used in a wide range of materials and applications. Commercial-grade Keyserts are available in carbon and stainless steel, both inch and metric series, and are supplied in Thinwall, Heavy Duty, Extra Heavy Duty, and Solid styles. Keyserts are offered individually or in kits.