Apparently the Boneweave Hauberk item creates a collision barrier when dropped on the ground. This blocks both players and monsters from passing. You can still teleport over the barrier, I'm not sure if other such things such as the barb leap attack work in the same manner.

Supposedly if you create a game one the Machines of War quest in Act 3, you can buy them from the "middle" vendor for ~150g. Also, you can buy magic versions on the AH for ~500g-1500g.

Abuse it while you can.