the normal modern use of a carabiner is as a connection link between two ropes pulling along the long axis. However historically there was something called a carabiner brake and it has many variations. You can rappel using a few carabiners with a wrap of rope around each and all connected together so that a pull on the end of the rope tightens the rope on the biner brake. Depending on the cordage you can put 2 or even 3 twists around the spine of a round biner. I reccommend leather gloves when doing this, and I practiced from my chimney before going off an edge. Remember most really light corddage is either brittle, stiff, or melts at low temperature, or all three.
Jim