This Standard is applicable to locking devices used with ball and socket couplings of string insulator units and used with the corresponding metal fittings standardized in IEC Publication 120: Dimensions of Ball and Socket Couplings of String Insulator Units, when they are supplied separately. When these locking devices are supplied with an insulator or fitting, they shall be considered as an integral part of it. In this case, the relevant tests shall be included with those of insulators, as specified in IEC Publication 383: Tests on Insulators of Ceramic Material or Glass for Overhead Lines with a Nominal Voltage Greater than 1000 V. On request, a certificate shall be delivered confirming that the tests on locking devices as specified in this publication, have been carried out. The locking devices are usually supplied with the insulators or corresponding metal fittings.