Professor Robert Van Pelt, "Professor of Architecture" at the University of Waterloo, Ontario (above), accepted in his expensively procured expert witness report for the trial of D J C Irving vs Penguin & Lipstadt that those holes are not in that roof slab now. In his expert report he writes:
"Today, these four small holes that connected the wire-mesh columns and the chimneys cannot be observed in the ruined remains of the concrete slab. Yet does this mean they were never there? We know that after the cessation of the gassings in the fall of 1944 all the gassing equipment was removed, which implies both the wire-mesh columns and the chimneys. What would have remained would have been the four narrow holes and the slab. While there is no certainty in this particular matter, it would have been logical to attach at the location where the columns had been some formwork at the bottom of the gas chamber ceiling, and pour some concrete in the hole and thus restore the slab. "
See David Irving closing speech, page 31.
Krema II, Leichenkeller 1, underside of roof