It may not be immediately obvious why we might want to create new intermediate categories of the kinds hierarchy. But there may be times, for instance, where we would like to make an action that applies in the same way to both containers and supporters, but to nothing else in the game. To avoid creating two nearly-identical rules, we would instead roll the two categories together into one, on the principle that duplicating source text is usually a sign of bad design.
So for instance let's say the player is able to zap objects to make them go away, but any contents -- things inside a container or on top of a supporter -- should always be left as residue. Here's one way we might do this: