Yeah I shouldn't admit it, but we've rapped off plenty of stuff on various epics using double 11s or 10.5s, and the added security and ease of setting and pulling the ropes more than makes up for the "extra" weight.
You never know on long all day routes when you're gonna get lost, who's gonna get sick or hurt, when the weather's gonna go to hell, when your partner's gonna drop the lead rack (seriously), if you're gonna run out of daylight, or who's just gonna chicken out and bail. I always like having two ropes--makes things like reepschnur raps seem gimmicky.

I've used this method often. I've even strung together 40' of various slings and cord with girth hitches before to do this when I was rappelling further than half a rope length (120' feet down, 60m rope) and didn't have a second rope with me... There's nothing unsafe about it if you do it right. Just like everything else, if you don't do it right... YER GONNA DIE!

There's nothing inherently unsafe about this method. Yes, a knot could pull through with the right knot and anchor. If you're concerned about it pulling through, back it up with a biner block. Someone already posted that method. If you're concerned about a biner hurtling 100s of feet and bouncing off rocks, dedicate a biner to that purpose. It will never see more than a couple hundred pounds of force. Or go even lighter and girth hitch a nice rap ring in there with a knot right behind it. A 6mm cord is a helluva lot lighter than another rope.

EDIT: Regardless of if you think it's unsafe, gimmicky, stupid, or whatever... LEARN HOW TO DO IT. What happens when you stick a rope and can't get it back? What if you get a core shot and don't know how to pass a knot? You could even string together P cord, shoelaces, webbing... anything. It just needs to hold enough force to pull your rope to you. It just might save you in an emergency.

For me, it adds unnecessary layers of complexity which may become difficult to implement safely under adverse or unexpected conditions.

Most mountaineering accidents occur on descent.

I'm sticking with two ropes. Have fun with the rope tricks.

Unnecessary levels of complexity? Really? Best case scenario it's the SAME rig as a typical rappel, just with cord. Worst case you add ONE biner.

I played with this last night. Of course testing/practicing on bolts on a home wall isn't remotely the same as actually being out in the elements, fatigued, sharp rock, etc.

With that said an alpine butterfly (for the biner block) and a locking carabiner together worked nicely (again at ground level with me jumping and pulling to test doesn't mean much in the way of overall experience). It pulled easier than 2 ropes joined as in the usual setup (I tested for ease of pull for comparison).

I'm not saying ill use this in any environment all the time but it'll be used by me I'm sure. A good method to have "in your tool belt."

I'm going to practice this weekend outside on bolts at Old Rag to see and if it works Ill bring it to the gunks and seneca and see how that goes.

If you wrap your friction hitch around both strands (6mm and rappel line) or just control the pull line really carefully somehow and with an alpine butterfly biner block this setup appears to be smooth (not gonna comment on safe as I havent used it yet).

The reepschnur method is nearly as old as rappelling. Nowadays, as Scott points out clearly, it is a poor alternative to twins and even half ropes, but of course not everyone wants to invest in the extra cordage and double ropes have never caught on in the U.S. anyway.

The recent Yosemite accident with the method involved a tragic lapse of technique and is not evidence of any intrinsic lack of safety. Set it up as in the Petzl diagram (which, as I said, is considerably older than Petzl) and its fine from a safety point of view.

Which is not to say that it doesn't have significant drawbacks. There are three main ones:

1. You are pulling your rappel with a 6mm line. If the rappel is hard to pull, gripping and pulling such a thin cord will make everything much harder, and yes, the biner around the bigger line can add friction to the system and so make everything a lot worse. How much worse depends on the angle of pull; diagonal rappels will have the most resistance. You might have to install prussiks on the 6mm line to enable you to pull on it effectively.

2. If your rappel hangs up after it comes free of the anchor, you are left with a 6mm line, which is to say you are left with nothing and may then need a rescue.

3. I'm always amused that people who complain that 8.5mm half ropes tangle too much then go out and use the reepschnur method with a 6mm tag line. When it comes to tangling, you ain't seen nothin' until you get a tag line properly clusterf#cked.

Of course, twins and halfs provide all kinds of additional features and margins of safety that are not available with a full-size rope and a tag line. The reepschnur system is probably best adapted to low-key populated settings on small crags where help is nearby, time is not of the essence, pull-downs are clean and unlikely to snag, and the consequences of a hung rappel are in any case not serious.

Yeah, people use it on Alpine routes too, especially when lots of rappelling isn't anticipated but the need for one or two full length rappels in an emergency seems real. A situation with a single rappel with a walk-off at the base, such as the normal rap on the Grand Teton descent route, is a good candidate for the reepschnur method. But if you use the method for multiple raps in a remote alpine setting, you should do it with your eyes open about the problems you could face and their consequences.

Good stuff rgold. Good points.

No passing. Just training. How do army soldiers train for battle when there isn't one? They "train as they fight." Seneca and gunks are where I "train" for bigger mountains and longer routes.

I can think of at least one reason why every climber should learn and practice the Reepschnur and the Carabiner Block. Let's say you're climbing with a single rope (60 meter) on routes with single rope rappels. You start to set up your rappel and notice that your rope is damaged about (15 meters) from the end. You will have to isolate the damaged section with an alpine butterfly. This will force you to pass the knot on rappel (yuck) or simply rig a single rope rappel with the Reepschur or the Carabiner Block. Both methods work, and the Reepschnur is the method shown by Petzel for use with the Gri-Gri. But; in my experience the Carabiner Block is easier to set up, has no chance of jamming in your rapid link/rap ring, and is much easier to pull.

That's wild. Those early climbers were smart if someone hadn't brought the reepschnur to my attention I dont think I would have ever thought of it.

If I ever carry an extra rope, I make it a thin half rope. Why carry 60m 6mm of accessory cord when you can carry 60m of 7.5mm cord and have the ability to climb on it. If you really want to go light then full half rope technique is best.

Solid point patto.