The Temporary Ledge
If your climber can’t unweight the rope, you’ll need to build a “temporary ledge” to clip the locking carabiner in front of the device. You'll need a shoulderlength sling and a locking carabiner. Here’s how:
1. Clip a catastrophe knot to your belay loop.
2. Build your autoblock backup above the catastrophe knot, on the brake strand.
3. Take another sling or cord and tie a friction-hitch onto the loaded, climber’s strand of the rope; clip a locking carabiner to it.
4. Take the loose, back-side strand of the anchor knot (the loose side of the rope going into the stack) and tie a Munter-mule-overhand (MMO) on the carabiner and sling from step 3.
5. Lever the blocking carabiner in the belay device back and forth. This allows slack to develop so the climber's weight comes onto the MMO/sling combination .
6. With the slack, clip a locking carabiner in front of the belay device and clip the climber’s strand into it; lock the carabiner.
7. Release the MMO and gradually load the device, which is now in LSD lower mode. Once the autoblock engages reliably, remove the sling/MMO, undo your catastrophe knot, and continue the LSD lower.