Abstract: As used with a nut, a device for indicating tensile strength comprises an annular groove approximately 1/8 inch in depth on the bottom of the nut adjacent to a washer. The same groove may be fitted in a bolt if the device is used with a bolt. A vertical shaft of the same diameter as the groove is also located within the nut or bolt engaging member and connects at one end to the groove. The groove and vertical shaft contain a "filler" material. A washer having a boss or protrusion is utilized with the engaging member wherein the boss or protrusion fits into the said groove. Once the washer encounters friction, when the combination nut and washer is tightened about a threaded bolt, with the connecting elements, the protrusion inside the groove pushes the filler up the vertical shaft as the nut rotates over the washer.