The progress capture (aka ratchet), is a critical part of a hauling system. It allows you to take your pulling tension off the rope to rest or reset, without the load sliding backward.
There are a few possibilities for the ratchet. Listed in increasing order of cost and/or weight:
plaquette style belay device (like a Black Diamond ATC Guide or Petzl Reverso)
Let’s have a look at the pros and cons each of these.
Note: especially for crevasse rescue, it’s really important to practice these different ratchet systems in the real world. It’s one thing to have them work in your living room floor, it can be completely different to see how they work under a lot of tension with snow being jammed up inside them.
Pros: free and weightless. (So far, so good!) Cons: even when it’s set up correctly the carabiners can get a little wonky and fail to lock up, so it’s not the most reliable system, in my opinion. Plus, it adds a HUGE amount of friction, making your haul a lot harder! Personally, I would maybe use the Garda hitch for some non-critical tasks like hauling up a backpack, but not in a rescue scenario unless it was really the only option. Read more on the Garda hitch here. (And yes, I know it’s best not to use screwgate lockers for a garda hitch, sorry about that in the photo . . .)
The classic method, and one still often used by guides, rescue teams, fire departments, etc. Pros: inexpensive, lightweight, can be improvised out of almost any kind of sling material. Cons: If it’s cinched down hard on the rope, it can add friction on to your pull. You always want the prusik to be loose when you’re pulling, but in the confusion and stress of a rescue this can be an easy step to overlook. Unless you have a prusik minding pulley, (also known with the great acronym of PMP), or an extra person sitting next to it with the unenviable title as “prusik minder”, or someone who’s coordinated enough to do both the hauling AND the prusik minding at once, the prusik can get sucked into the pulley and cause all kinds of problems. Plus, every time you slack off from pulling, unless someone slides the prusik back toward the load, the load is going to slide backwards the length and stretch of the prusik loop, which can mean when you reset your pulley you’re losing a foot or so of hard-earned lift. Your partner stuck in the crevasse will NOT appreciate being a dropped a foot or two when this happens.
An old-school Crafty Rope Trick (CRT), if you don’t have a prusik minding pulley or just a carabiner at the anchor: run the rope through a tube style belay device like an ATC before you clip it through the carabiner. The belay device keeps the prusik loop from getting pulled through the carabiner. It actually works surprisingly well, give it a try. But it does add a bit more friction. See photo below.
Black Diamond ATC Guide
(or similar style device). If you set these up in autolocking belay mode, the rope will slide through as you pull, but when you let go, will lock down immediately. Pros: no loss of progress when you stop pulling. Cons: A LOT of extra friction, an extra piece of gear you may not have with you, especially on a glacier climb.
Functions pretty much the same as the belay device as mentioned above. Pretty much the same pros and cons also, and you’re very unlikely to have one with you in a crevasse rescue situation. Fairly high amount of added friction. But for a rock climbing scenario, these would work okay. A Grigri also has the benefit of being able to release under load, which can be a great help if you flub something up and need to release tension for some reason.
These little suckers have a high efficiency pulley combined with an ascender type spring loaded rope grab. They give you a great easy pull combine with zero loss of progress . Pros: work perfect. Cons: cost about $100, ouch! (Kind of a lot for seldom-used rescue gear, IMHO . . .) Traxions come in various flavors: the Micro, the Mini (the one I have, in the photo below, now discontinued) and the Pro. For alpine climbing, you want the Micro.
If you’re doing a 1:1 haul of fairly heavy bags on a big wall climb, you probably want a slightly larger diameter pulley wheel to get a small increase in efficiency. One popular ratchet pulley for big wall climbers is called the Kong Block Roll. (I do not have one, but word is they work great.)