The modular structural coupling for the construction of variable skeletons from hollow profiles is assembled from modules, i.e. from a central module (101) and an end module (111), possibly also from an angle module (301, 302, 303) or a hinge module (304). The modular concept makes it possible to create couplings to connect profiles into skeletons of many dimensions and shapes, such as supporting structures of instrumentation, laboratory and research systems, and use in other areas such as healthcare, construction, engineering, space applications, design and others can be assumed.