Shorten a sling with carabiner wraps
Often it's handy to temporarily shorten a sling or cord by just a cm or two, typically done when anchor building. Doing this can help fine-tune anchor load distribution by shortening the arm that's going to your strongest piece, adjust a cordelette if the direction of pull has changed a bit, or shorten one sling if the bolts you’re clipping are not quite in the same horizontal plane.
One easy way to do it is to simply wrap the sling a few times around the carabiner. With a skinny Dyneema sling like this, each wrap shortens the sling about 2 cm.
Probably best not to use more than two wraps. If you need to shorten your sling more than that, it’s probably time to rerig your anchor.
Other methods: put some twists in the sling, or tie a clove hitch.
Safety note: Don’t do this unless you're dealing with a completely static anchor. If you do this on lead the sling loops can loosen in such a way as to slip down over the gate and then when loaded can open the gate. That may be hard to visualize, but if you take the setup below, and jiggle it around a bit as might happen on a long pitch, and then just keep randomly loading it, one of those extra wraps could loosen up, slide around, and potentially open the gate.
2023 Update:
I’ve received a few frosty comments on this technique over the years, most of them saying something along the lines of “this is going to weaken the carabiner, because you're putting the load closer to the gate”, or something like that.
I was curious if this has any merit, so I had my buddy Ryan at HowNot2 test this. Guess what?
It DID NOT weaken the carabiner
It DID weaken the sling.
Ryan did two different break tests on this with a Dyneema sling. First test the sling broke at 12.4 kN, the second test is broke at 15.4 kN. The sling was rated (I think) 22 kN.
Would this be different with nylon? Probably. Is this concerning? Maybe. Does it concern me? Not really, because these numbers are still significantly higher than you're ever going to see in any recreational climbing situation. But it’s still an interesting data point that I wanted to share.
I don't think I can embed this short form YouTube video in my webpage, so here's a link to see it yourself.
Screen grab from Ryan's video is below.
