Variations of this have been around since pretty much forever, but the subtleties of putting the bar tack at the bottom and offsetting the top step are from the excellent aid / big wall book, “Hooking Up”, by Pete Zabrok and Fabio Elli.

• Need to pull a few a few moves of “alpine aid” to get past a difficult spot? (There goes your onsight, sorry.)

• Maybe it started raining, the rock is wet and slippery, and you decide that the best way to continue going up is the aid climb rather than free climb.

• How about quickly making a “ladder” to help someone climb over the lip of a crevasse?

Here's how to quickly make an aid ladder out of two slings. (If you don't have a 120 cm sling, you can do the same thing with three 60 cm slings.)

While a skinny Dyneema sling works, it’ll be easier on your feet to use a wider nylon sling if you have it. (But hey, this is improv, use whatever you’ve got.)

Even if you have to make a few aid moves in a row, you should only need one aider. Basic sequence: Place some gear, clip the aider to it, climb up the aider steps, clip a carabiner or quickdraw from your belay loop to the gear and hang from it (aka fifi hook), remove your aider, repeat as necessary.

1 - Start with a 120 cm sling. Put the sewn part on the “bottom” of one half of the sling. The bar tacks cause the sling to open up a bit when it's hanging, making it easier to step into. It helps to actually put your foot in the sling and step (gently) on the bar tacks, to keep them in the right place and put a bit of tension on the sling as you do the next steps.

2 - Tie an overhand knot in the sling, about at the midway point.

3 - Pull down some sling material to make the top step offset a bit (this makes it easier to step into) and tie a second overhand knot, making a very small loop. The second overhand knot keeps the top step open. You could stop here if you’re fairly short and/or have great hip mobility. However, adding one more step to the aider makes this work much better.

4 - Girth hitch a single length 60 cm runner into the top of the double runner. Try to keep the bar tacks on the bottom as shown. Tie another overhand knot as before, with a little bit of extra material on one side, making an offset loop.

Schweeeet! Now you have a three step aider, and it's hopefully long enough for you to reach to clip a high placement and still reach the bottom step with your foot. If it's still a bit short, clip a quickdraw to the top to extend it a little bit.