In Untitled [black painting with portal form] the canvas does not wrap around its stretcher on all sides. This view shows a section of raw canvas attached to the top of the stretcher with a nail. When Rauschenberg began his Black paintings, he often hung them in doorways and windows while he worked. In keeping with this practice, Untitled [black painting with portal form] was likely nailed to its stretcher after it was completed. See figure 2 in the essay on Untitled [black painting with portal form] for a view of the painting in its early state.