Abstract: For the erection of frames and mounting structures for apparatuses there is provided a set of profiles with half open grooves. The grooves serve for the mutual assembly of the profiles by means of nuts and bolts which are introduced in the grooves. A ground profile is provided with grooves in such a way that further profiles may be easily secured at the desired levels. For realizing of corner joints, a corner angle piece is provided with inclined bolts acting toward the angle part of the angle piece and penetrating into the material of the profile.