on the cusp of empty (idea)

The (almost always food) container sits, recumbent, on its shelf or niche or table, a sparse sample of the contained substance barely coating the inner surfaces. Peanut butter jars with a smeary ring of brown spread around the upper circumference, just below the lid and beyond the reach of a table knife; gallon jugs with a whisper of milk covering the bottom, mocking in their near-absence.

These are vessels on the cusp of empty. Not actually empty; but without enough quantity to be useful in any endeavor. For some reason, informal tribunals will often decree clemency on an offender who returns such a container to its place of origin without refill or replacement, citing that "There's still some left." or "It's not empty...see?" in defense, sketchy though it may be.

Technically, a roll of paper towels or toilet paper (excuse me...bathroom tissue) with three or less squares (or triangles if you have that bizarre French TP) is also on the cusp of empty, but since there is an element of distress involved in leaving such a condition for the next user (uncontrollable spills or an unwipable cleft) most courts will find in favor of the plaintiff and demand swift reparations by the transgressor.