Our contractor framed in two huge holes in the long hallway, in order to provide access to the under-eaves area for storage and to get at the AC unit. Unfortunately, they were made inordinately large. We've been at a loss as to what to do with them for a long while now. We considered doors, swinging bookshelves, panels, and the like, and finally settled on installing a wall mounted cabinet into the hole. Wall mounted since they typically don't have the extra just-above-the-floor construction.

Having made our plans, now we just needed to downsize the gaping hole to accommodate the new cabinets. They're both in slightly different states of being done.