Abstract: This invention relates to a locking device for nut/bolts, which is a locking assembly to be positioned between at least two nuts/bolts, to which have been fitted at least two brackets equipped with an inner race polygon, to the outer periphery of which has been fitted a fastening cam for the spring element to be fitted between the brackets. There are at least two of the fastening cams on the brackets and the locking device is fitted to be formed of at least three brackets chained with each other by spring elements, of which at least one is furnished to tighten the nut/bolt of the target of fastening symmetrically. Further, the invention applies also to the installation device for the locking device.