The invention concerns a half shell element (10) for the production of a hollow body with an identical further half shell element (10), with at least one guide (20 . . . 20′″) for the further element (10), which is constructed in the region of a first half periphery (11) of its encircling edge (12), so that the further element (10) can be pushed onto the half shell element (10) from the second half periphery (11′) of the edge (12) lying opposite this first half periphery (11) and guided on the edge (12) and held in a final position. The hollow bodies which are thus produced can be both inserted into steel cages and also connected with each other via bars and built into concrete layers.