The present guideline, based as it is on the ISO 5393 standard, is intended to provide users of threaded fastening elements with a procedure for evaluating or formulating specifications for the performance of power-operated assembly tools and enable the manufacturers of power-operated tools to offer their products on the basis of correlated technical specifications. The present guideline defines a laboratory performance testing procedure for power-operated assembly tools used for installing threaded fastening elements. It provides instructions on what should be tested and how this should be done, and also on how the test data should be evaluated and presented. It applies to tools which deliver an uninterrupted torque course. It does not, however, apply to impact wrenches, ratchet wrenches or wrenches with a ratchet clutch nor to other tools which screw in the fastening elements in discrete steps, overcoming static friction at each step, particularly because the torque generated by tools of this kind cannot be measured with conventional measuring instruments.