The vid is HD, so go to youtube if you want.

HOW THE GLITCH WORKS

Objects that are dynamic when hit by large physical forces, such as an infected Tank or a large explosion, can be simply moved by hitting it (not exploding it) with a: Oxygen tank, Propane tank, Gasoline tank. When one of those objects stated in the 1st sentence are hit by a thrown object (propane tank, etc.), the large object is suddenly very dynamic to the push of a player.