Daughter bought new house. At rear of garage a black lead comes out to connect to a plastic fitting. It's a black plastic capsule with a clear top. Inside are a couple of cubes one yellow and one blue. What is this?
It sounds like it might be some door opening/closing mechanism, but without an actual picture it's hard to tell. Can you see where the other end of the lead goes?
If you upload the picture to http://tinypic.com/ and then you'll get a link to it that you can post here. Just click Browse on that web page, find your picture on your hard drive, and then click Upload Now.