Loctite threadlockers loctite 135331 loctite 221 has been designed for locking and sealing threaded fasteners which require easy disassembly with standard hand tools it cures when confined in the absence of air between close fitting metal surfaces and prevents loosening and leakage due to shock and vibration loctite 221 is particularly suitable for applications such as the adjustment of set screws small diameter or long engagement length fasteners where easy disassembly is required with