Tying or trapping sling to krab has some warnings:
Sling can't rotate freely to even wear, nor in some cases to pull evenly on each leg.
Also the trap/binding; can make it look like sling is secured on krab, but can shear thru trap/binding and come off:
mytreelessons.com/rl/images/krab_loading_captive.png
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Here in this old pic i show usage, and kinda brake my own rules, but notice even then:
skinny sling harder to not notice when kicks leg of sling hi/over to inside krab/err
Has 2 turns that must 'undo' for this fault
Turns must come off in opposite directions!
Err would sit much higher than sling, when lays across captive eye:
mytreelessons.com/Foins.JPG
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i love slings as a reusable, multi-purpose modular component.
Can swing sling/krab around branch standing on and catch krab thru sling/pull / already choked(all 1 handed); clip to rig line in other hand, pretty much in 1 motion.
Always kept DBY in end of line, usually clip to belt with STEEL krab for throwing weight too.
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Slings, krabs etc. used to be extra stuff would only call to be sent up if needed.
Biggest learning jump was taking them up with me, and finding the ready usages for them waiting / not waiting for them to be sent up!!!