Yesterday a Piano Technician came to install a Dampp Chaser on our piano. When he drilled little holes into the piano I was a little worried but I know he knew what he was doing. I watched for a little bit but I left the room so I could watch Victorian Farm on www.tvo.org
The Dampp Chaser is supposed to control the humidity of the piano. Wood will shrink and swell when the humidity changes. The piano won't hold it's pitch as well if the humidity changes and the wood parts might crack. That's why my parents decided to get the Dampp Chaser for my piano.
Here's a picture of what it looks like.
It's inside the piano.