I purchased these to make attaching my tarps to the trees a little simpler. I used to have the ridge line attached to the tarp and used a truckers hitch or some other knot to tighten the lines up around a tree or pole. Now I reverse this. I use a bowline knot to quickly hitch to the tree and attach the Figure 9 biner to the tarp tie outs and then quickly tighten up and center up the tarp. Takes seconds to do and almost as quick to undo.
I do suggest a backup knot of some kind once everything is set. Under high loads some cords can start to slip. With a slippery half-hitch the thing is solid and does not move.
Well worth the small weight penalty to me.