Scaffolding systems should have the facility of building extensions to it when needed. Yet required extensions, while using the known systems, are not feasible since mounting and dismounting possibilities are not provided for except for mounting and dismounting complete scaffolding floor stages. Intermediate mounting or dismounting cannot be effected while using known systems. The invention provides for an interlocking scaffolding system which also facilitates unlocking of platforms and flattened end sections 14 of struts 3,4 thereby maintaining all required stability of the cooperating scaffolding parts having been erected. This is achieved by the the function of angular rotational movement between the interlocking member parts of a joint i and inherent use of special brackets 12 for not only interlockingly clamping platform ends to the bracing frames but also by the additional use of special brackets 12 for interlocking flattened end portions 14 of struts 3,4, each having its own matching opening 15 passing over a recessed protrusion which is welded to the standard or post of the bracing frame, whereafter an interlocking nose or cam member 16, integrally forming part of said matching opening 15 is hooked in, thereby blocking said recess 13. The matching opening 15 is so no longer allowed to give free passage to the protrusion 12 any longer, thereby giving an immediate interlocking function. For interlocking the platform end sections to special brackets, a similar angular rotation is required while positioning or taking away the platforms, which in their ultimate operational position are automatically interlocked with respect to said brackets.