A metal flap installed at the bottom of the bowl of a chemical or pit toilet, which blocks out unwanted odors. The flap is hinged and sprung in such a way as to only open when a certain amount of weight is applied to it.
A common accessory for this device is the stoker - a small stick which is used to manually operate the flap, should it for some reason fail to open.
"I say, Thomas, would you be so kind as to pass over a stoker, I have produced a rather large stool which has become lodged in the shitflap".
A "Toledo Mud Flap" occurs when a man has anal sex with a woman (or man, if that's your thing) who has diarrhea. The man's testicles act as a mud flap, keeping excrement from splattering all over the room.
David has given the Toledo Mud Flap to a fat girl this week.