a point between 2 magnets, what remains constant at that point?

a fixed spacial point between 2 fixed magnets. if I place different blocks of material on that point, is the H that will remain the same? or is it the B? or just the MMF (magnetic motive force), while B and H will always change depend on the material placed?

the same question for E, D, and EMF between 2 fixed charges.

thanks