The Lourdes-Lok (see Figure 1) is a unique patented self-locking fluid fitting design that incorporates a redundant locking scheme to prevent loosening of a fluid fitting joint.. The locking feature, which is independent of the threads, creates frictional forces and a prevailing torque that resists self loosening of the nut. The design also incorporates a secondary fail safe locking feature of the nut from the fitting. In addition, when installed the device is visually verifiable as being present and functional. The Lourdes-Lok eliminates the need for lockwire on fluid fitting joints, which reduces maintenance time, life cycle costs and improves operational readiness. Compared to standard fitting installations where the fittings are not normally lockwired, incorporation of the Lourdes-Lok will prevent operational loosening and reduce leaks. The Lourdes-Lok is capable of maintaining the joint integrity over the operational service life of the fitting installation, which improves the system reliability and safety.