Rapier case

From Cunnan

A case of rapiers is a matched-pair of fencing weapons (levels of "matched-ness" depend on the person). The name comes from the fact that they used to make the pair of rapier in a way that they would both fit into the one scabbard - a case.

This is also known in the SCA as fencing Florentine, and some people call it "fighting two-swords."