caging the cork...

...and then releasing the 'pop', the muselet (wire cage) secures the cork in the bottle keeping it sealed to the point of drinking.
The muselet (wire cage) is made of three parts assembled as a single piece: the lower ring (ceinture), the body of the cage itself consisting of four separate legs and a top of soft wire topped by a metal, circular cap (plaque).

There is of course a wonderful history to the muselet and yes Dom Perignon, he of 'tasting the stars', is part of the story.
Here is more