enclosing

That which encloses.

And he made the breastplate of cunning work, like the work of the ephod; of gold, blue, and purple, and scarlet, and fine twined linen. […] And they set in it four rows of stones: […] the fourth row, a beryl, an onyx, and a jasper: they were enclosed in ouches of gold in their enclosings.

The act or situation by which something is enclosed.

Duane Duck is a play of boxes, explicit and implicit, frangible or firm; indeed, Duane Duck is a play about boxes, a performance of all manner of relations to enclosings.

Of a region, containing all points of a given set within its bounds.