This is a hack. It is really based on a very old hack, a loophole that he found years ago when he was trying to graft the sword-fighting rules onto the existing Metaverse software. His blade doesn't have the power to cut a hole in the wall—this would mean permanently changing the shape of someone else's building—but it does have the power to penetrate things. Avatars do not have that power. That is the whole purpose of a wall in the Metaverse; it is a structure that does not allow avatars to penetrate it. But like anything else in the Metaverse, this rule is nothing but a protocol, a convention that different computers agree to follow. In theory, it cannot be ignored. But in practice, it depends upon the ability of different computers to swap information very precisely, at high speed, and at just the right times. And when you are connected to the system over a satellite uplink, as Hiro is, out here on the Raft, there is a delay as the signals bounce up to the satellite and back down. That delay can be taken advantage of, if you move quickly and don't look back. Hiro passes right through the wall on the tail end of his all-penetrating katana.