Part 2 - The Underside Kind

An underside is a kind of container. The carrying capacity of an underside is usually 10000. [limit by bulk rather than quantity]
An underside is usually closed. [so that it conceals its contents]
An underside is usually privately-named [players should never need to refer to these objects directly.]

The printed name of an underside is normally "[printed name of the holder of the item described]"

The specification of underside is "An underside is a special kind of container that represents the space under an object. To use it, define an object of kind underside and make it a part of the thing you want to be able to put things under."