To optimally fix the knife-edge square for measurement, it is fastened on the universal and precise ground plate SQUARE-base with a clamping bracket. In order to ensure a consistent sideway position it is additionally recommended to use the vacuum injected alignment aid SQUARE-tool. The required vacuum connection for this tool is already integrated in the squareness measurement devices from Kunz precision. For the concise recording of the measured data optionally the user friendly and practice-orientated PC-analysis programme STRAIGHT-soft for straightness- and squareness measurements is available.