ESDU 14002, which supersedes ESDU 87023, gives guidance on fastener devices commonly available to prevent joint loosening under severe vibration in service. The bolted assembly is designed with the bolt(s) pretensioned to a prescribed load (see ESDU 14001), and the methods of maintaining that pre-load are considered. In particular, the double plain lock nut is examined and tightening procedures recommended. The influence of tolerances on the pre-load are considered, using a worked example. The effect of vibration cycles on loss of pre-load in a lock nut arrangement is shown and compared with the use of a single plain nut. This comparison is made in terms of a fatigue stress-endurance curve. Additionally, the results of over 1320 loador shear-displacement tests are presented as endurance curves, showing the loss of clamping force during transverse shear loading in joints with different nut and bolt combinations.