Other than screaming Mommy, you have options:
Belay Without a Device
Use a locking carabiner and a Munter hitch, popularized in the 1960s by the Swiss guide Werner Munter. This easy, bomber knot has 2.5 kN of holding power when locked off—versus the roughly 2 kN of most belay devices. Ideally, you’ll have a pear-shaped HMS biner, which easily fits two bends of the rope. First, draw the rope through the biner, and form a bight with a half-twist. Flip the bight another 180 degrees and clip it into the biner (fig. 2). To lock it off, bring the brake-hand strand parallel with the side entering the biner (fig. 4). To rappel (with double lines), form the Munter with both rope strands together. Caveat: Keep the knot clear of the biner gate to lower the risk of opening. Oh, and Munters kink ropes to an unholy degree, so use them sparingly.
Climb Without a Harness
Let’s say you took it off to pee…in a windstorm. Whoops! Or, more likely, you just didn’t bring it, not realizing your “fourth class” objective was actually 5.6. You still have options. Back in the day before harnesses, climbers tied the rope around their waists with a bowline on a coil. This method can snap ribs in a big fall, but it works in a pinch. Bring the rope snugly around your waist at least three times, leaving two to three feet of tail. Form a bight with a half-twist. Bring this under and back through your waist coils, then tie a bowline with the tail. Add an overhand backup with the remaining tail (fig. 4). Voilà, you’re ready to climb. Comfort tip: Jerry-rig leg loops by girth-hitching slings around your gams; clip them to all of the waist coils.
Rappel Without a Harness
Say—blackest of horrors—you must rappel sans harness. It’s time for the Dülfersitz. Here’s how: Straddle the rappel ropes, bringing them back around one leg and across your hip, then up over the opposite shoulder. Now bring the rope down and across your back, where the brake hand holds it beside the wrapped hip. Step backward over the edge, and use your brake hand and the rope’s cross-body friction to meter your descent—go slowly! While the rope’s friction is punishing (pad your clothing accordingly), rope rash beats an appearance in next year’s volume of Accidents in North American Mountaineering.