Abstract: The invention concerns a device for indicating the tensioning of a fastening member, such as a screw or the like, said device comprising a first portion with a first fastening member receiving aperture; a second portion with a second fastening member receiving aperture in alignment with said first fastening member receiving aperture, and a joining portion connecting said first and second sheet portions allowing the first and second portions are biased towards each other by the head of the fastening member in response to the tightening of said fastening member, wherein the device is provided with irreversible indicator means for indicating that the tension in the elongated fastener during the mounting process has been exposed to a tension exceeded a predetermined tension value, and wherein said irreversible indicator means comprises that said first portion is provided with a distal end portion adapted for sliding and locking engagement with corresponding indicator means provided on the second portion, and that