After a Axis player takes out your favoutite unit with either a mortor crew or a PAK Anti-Tank Gun, you would send your Half-Track Quad behind the Axis player's weapon and flank them. This is called Ninja Quad
Jeff: What's that behind your Anti-Tank gun?
Noob: OMGZ! You killed my PAK Anti-tank gun with a quad!
Jeff: LOL, Ninja Quad FTW!!