Willis Hatch 

The hatch in the roof of an elevator through which an action hero can suddenly enter, wearing a slightly dirty white singlet, to attack bad guys or rescue trapped victims.

N.B. these portals only appear in bad Hollywood films, rather than actual, real-life multi-storey buildings.

"With a crash, the Willis Hatch burst open and John McClane dropped through, knocking the terrorist to the ground."

Willis Hatch by dom Kaos October 2, 2009