The invention relates to system for the mounting of shelves on a substantially rectangular load carrier having four identical columns arranged in the corners thereof. The system comprises columns having a rectangular profile with four side faces, a substantially rectangular shelf of a length which is shorter than the distance between the columns of the load carrier, on which shelf a holder is mounted that can be inserted into complementary slots in the columns of the load carrier, said slots being configured with a support face with which the holder is capable of engaging in such a manner that the holder supports on the column. The columns as such are configured with slots that extend symmetrically about a longitudinally extending center axis of one of the side faces and through the side faces adjacent to that side face. The slots are each separately configured with three substantially identical cut-outs, the one of which is situated in the axis of symmetry and the two remaining ones are in the adjacent side faces. The cut-outs are function as support faces for the holders of the shelf, them being arranged on the shorter sides of the shelf and extending in the longitudinal direction of the shelf to the effect that they are capable of engaging with the slots in the four columns arranged on the load carrier.