Corking machines are the cork stoppers used in wine bottles to seal the contents of the bottle. They are made of cork, a natural product obtained from the bark of the cork oak. The cork stopper is secured in the bottle by pressing it into the neck of the bottle, creating an airtight seal that protects the wine from oxidation. Corkers have long been used for wine bottles because cork is a very good sealant and allows the wine to develop and breathe while it is stored in the bottle. However, there are other types of wine closures such as screw caps or glass stoppers that can be used in some cases.