If you've never had the opportunity to taste wine directly from a barrel, you are probably not familiar with a wine thief. No, it's not someone out to steal wine. But it is a device that could be used for such a purpose.
A wine thief is typically a glass or plastic tool used by wine makers to remove a small amount of wine from a barrel for testing or tasting.
It works by simply dipping the device into the wine and then holding a finger or thumb over the opening at the top to trap some of the wine in the tube. The technical term is pipetting. But it works by creating a partial vacuum above the wine-holding chamber to allow the wine to be drawn out. When you remove your finger, and hence the vacuum, it releases the wine either into a glass or testing vessel.
A quite simple device that makes drawing wine out of wine barrel extremely easy.
So, next time you are visiting a winery and get a chance to get into the barrel room, ask to see a wine thief. Or, better yet, ask to see it demonstrated. You just might get a taste of wine directly from the barrel which can be quite a treat.