Note: This really isn't a carabiner knot, but it fits better here than it does with the Semi-mechanical Ascenders.
Franz
Bachmann developed the Ring Knot in the early 1960s. It adds a
metal ring to the Hedden
Knot, reducing friction so that the knot can tighten and especially
loosen easier. The ring also reduces the risk of binding that
one has if they mis-tie the Hedden.
You can vary the number of wraps to change the knot's holding power. If you need some extra holding power, try tying a half-hitch below the Ring Knot - but don't expect to be able to move the knot as easily, since the half hitch interferes with loosening the knot.