It's one of those things you would have to see to believe. It involved no conscious thought. I just reacted. Picture this. This particular tub had not been put in a rack yet. I use Hefty tubs which have very good lids. I have the tub on the floor with the lid half open. Drop medium rat in. Rat walks over like she is going to sniff my beautiful albino girl and chomps her right in the side. I already have the lid in one hand. Free hand shoots in and grabs the rat by the tail at the same time pulling it backwards out of the tub. At the same time I am pulling the rat out of the tub my other hand is moving the lid down. About the time that the lid is almost shut the rats head is in the tub and his body is not. Hit the top of the lid at the same time jerking rearward on the rat's tail and you end up with a rat with a broken neck. This all happened in under a second.
I don't think I would recommend this as a technique. It is just what happened. I don't even know if it is repeatable.