Through the development and application of high strength geosyntetics, the problem of clamping during the tensile test has become an important theme. The construction of clamping systems is decisive for obtaining a value as close as possible to true tensile strength. For this purpose the theoretical demands on an ideal clamping system are depicted and the development stages of the clamps are shown. The results of tensile tests with different clamping systems are given in Table 1. Infrared images are given to show stress/strain inhomogenity.