Keep dirt and bugs outTell us more. What are you looking to accomplish? -Skip
Keep dirt and bugs out
Seriously now (I know I've poked a couple frivolous posts above) ...
Not knowing what type of plane you have, or the setup for your carb heat system, there isn't a way to answer your question. Need more information.
I fly an experimental and it is set up so that all carb intake air goes through the filter. When I pull on the carb heat the cold air (exterior) inlet is blocked and the warm air is taken from a carb heat shroud (muff) mounted around an exhaust tube. There is no reasonable way to plug that opening as it is difficult to get at without removing the cowling. If you are looking for a simple plug for the air intake we would still need to know the type of plane/intake that you have.
The carb heat in a Lycoming-powered 172 comes off an exhaust riser and there is no port to plug and you can't get at it anyway. In the Continental-powered airplanes, there was an inlet in the baffling right behind the cowl opening. Two of them, one for carb heat and the other for cabin heat. I wouldn't go plugging either of them, since a forgotten plug means a badly overheated muffler that will burn out and fail and cause lethal inflight problems like fire or carbon monoxide poisoning.Ok thanks for all the responses I mean like when it is in the hangar like a cowl plug sorta thing I have a 172