While quite slender cross bracing may suffice to maintain rigidity in a braced structure under static loading conditions, during an earthquake progressive slackness develops in the bracings, resulting from overstrain in tension, which gives rise to increasing horizontal movements and degradation. In this paper tests are described on devices, fabricated from round bars and located at the centre of the bracings, which allow repetitive overstrain to occur without the development of slack. It is postulated that, for a stable condition of cyclic overstrain, the device shall be of the same shape as the frame to be braced, and most usually fabricated in steel rod or bar. Successful tests were carried out on such a device in a square frame.