In reply to tabasco:
There's also a simpler way to do the clove hitch and Italian hitch on a hanging karb one handed. Very useful at the anchor.
Italian hitch
1. Clip the rope onto the karb as you'd clip a runner. Say the gate opens on your right and you're using your right hand to clip.
2. The rope behind the karb should be further to the gate than rope above. Hold the rope behind with your right thumb pointing down.
3.Bring the back rope over the front rope and clip it into the gate with your thumb pointing up and towards yourself.
Clove hitch is the same as above, except in step 3 you do an extra twist and clip the rope with your thumb pointing up and away from yourself.
With this method you need only two fingers to do the two knots. It's the quickest way and can be done with big mitts. It works with the gate pointing either way and with either hands.