The Bachmann knot is used to support a load on a vertical rope. It slides down the climbing rope freely, but solidly grips the rope when loaded. To release the knot you just need to unclip the top loop and pull the line free. It is safer to use the knot with the carabiner gate opening facing down.
Fold the rope in half, creating an open loop.
Unlock the carabiner and insert its top segment into the loop.
Turn the rope around the cord and the carabiner’s long segment.
Turn 4-5 more times to wrap the carabiner’s long segment. Lock the carabiner.
The Bachmann knot is complete.