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 load- or 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.