 When the tube is in the box, it can be seen through the window which normally has a grille or patterned lattice on it.He starts by lifting both items onto a table which is raised off the ground (no trap doors) and then shows them empty both separately and together by lifting them off the table in turn, and looking right through the tube/box at the audience, putting his arm through and moving it around etc.When the tube is lifted out of the box, the black empty interior of the box can be seen through the grille.