Oh, I'm sorry. That was a typo. It should have read "carabiner." (also spelled karabiner I believe)
They're basically a metal loop with a clasp that can be threaded through things. Real ones are used for climbing and ropework, but low-grade (meaning weaker and generally less secure) ones are sold for use as key rings and the like.
I guess, think of it as a small lock without a combination or key
Pictures would be great! Thanks.