Duchamp had originally intended for the Boîte to contain a third plastic element: a reproduction of Glissière contenant un moulin à eau (en métaux voisins) [Glider Containing a Watermill in Neighboring Metals], a preparatory work for the Large Glass made on a roughly semicircular pane of glass that rotated about its straight side on a hinge.¹ 

In the twenty numbered Boîtes-en-valise, Glissière appears fastened above 9 moules mâlic on the far edge of the Boîte's right pull-out, attached with clear adhesive tape so that it could glide back and forth about its straight side like the original work and could be tucked in parallel to the pull-out when one wished to close the box.² Due to the warping of its plastic, however, which kept it from lying flat against the right pull-out and thus prevented one from drawing in the pull-out and closing the Boîte altogether, Glissière grew so physically problematic in the Boîtes which featured it that by 1955, Duchamp decided not to include it in the rest of those which remained to be assembled.³ His response to this conflict between the Boîte’s architecture and one of its most volatile materials suggests that Duchamp did not intentionally imbue the Boîte with the self-destructiveness which many of its copies so brazenly exhibit today, and that he would not approve of physical changes to his Boîte that interfere with the smooth unfolding of its display.⁴