The "Nite Ize Figure 9 Carabiner" looks a bit precarious: a toothed hook holds the loose end of a rope in place, making lashing as simple as a couple of quick loops. But Timothy Lord, writing for Cool Tools, has found the $5 bits handy for lots of jobs, including hauling a kayak around on his car.
Thus far, I have used the devices only with standard-issue parachute cord, but they're sized to work with a range of small-diameter ropes. Though the tying system looks suspiciously wimpy, I've found it is as robust as promised. I ordered the Figure 9s to replace the mesh netting that came with the roof-rack basket on my car. Not only do these make a decent replacement (i.e. riding around with a kayak strapped to my car this summer), but tying one more knot under the car is something I'm glad to skip.
Not for climbing! It says so right on the aluminum clip.
Nite Ize Figure 9 Carabiner [KK.org]