Not quite sure if this is what you mean, but I maintained a bank of Omega D5-XLs for 20+ years. The lamp housing (and condensers) is lowered down onto the negative carrier placed on top of the lens stage. I was forever alligning negative stages because, despite verbal and written warnings, students would let that heavy lamp house slam down onto the negative stage after they removed their negative carrier.
And I was probably tightening those screws on the negative stage a lot tighter than Mal! LOL!