One of the recommended methods is as follows:
Prior to the test a very small mark should be made near one of the ends of the parallel length. Using a pair of needle-pointed dividers set at the gauge length, an arc is scribed with the mark as the centre. After fracture, the broken test piece should be placed in a fixing clamp and axial compressive force applied, preferably by means of a screw, sufficient to hold the pieces firmly together during measurement. A second arc of the same radius should then be scribed from the original centre, and the distance between the two scratches measured by means of a measuring microscope or other suitable instrument. In order to render the fine scratches more easily visible, a suitable dye film may be applied to the test piece before testing.