Or you could lash the center with dental floss like this:
...
PS: I stole that link from maculated's post a few years back.

Or you could lash the center with dental floss like this:

http://www.inquiry.net/images/whip.jpg

If tight, it holds for a few months depending on how much wear your rope gets. Then you have to pay to replace the very expensive and hard to come by dental floss. :lol:

As to JA1484's assertion that a 50% reduction in rope strength just means a 50% reduction in the number of falls it will hold before failing, my head is spinning. Maybe someone with more patience than I'm feeling can explain how completely and utterly wrong this is for so many reasons.
One might start to understand by looking at it this way, however:
Imagine a ten fall rope that starts out with a breaking strengt of 6000 pounds. The rope is then cut, or treated with acid, so that its strength is reduced to 10% of its former value, or 600 pounds. Do you really think this rope is still good for one really hard fall?

Marking of Ropes by End-users
15.05.2002 11:00

End-users of climbing ropes have been marking their ropes to help rope management. At the last Plenary Session the Safety Commission, together with the attending rope manufacturers, dealt with this problem. It was concluded that certain products act aggressively on polyamid. As a result the Commission has published the following NOTIFICATION:
Notification Concerning the Marking of Ropes
Tests done by the UIAA Safety Commission and some rope manufacturers have shown that marking ropes with liquids such as those provided by felt-tipped pens can damage them; even with those markers, sold specifically for marking ropes. The test results have shown a decrease of up to 50% of the rope strength, more correctly: of the energy absorption capacity of the rope (expressed by the number of falls in the standard test method in accordance with the UIAA Standard101).
Therefore the UIAA Safety Commission warns against marking a rope with any substance that has not been specifically approved by the rope manufacturer of that rope.
It is not possible for the UIAA Safety Commission to test all markers that are commercially available and can be used for marking ropes. Furthermore it would be impossible for the UIAA Safety Commission to keep such information up-to-date. In addition, the effect of any rope marker seems to vary with the make of rope. Hence, all the UIAA Safety Commission can do is to warn mountaineers and climbers.
Issued: April 2002
News
UIAA Standards

Metolius is now selling Monster Ropes. They have this really cool middle marker feature. Two bright pink strands of nylon sewn through middle. They also have a single strand of red yarn 30 ft. from either end. This is really handy (pun intended) for rappelling. You can feel the markers go through your hands letting you know that you are near the "end of your rope".

The 30 foot marker would be good for warning your leader that there is 30 feet left in which to find a good anchor.

My main complaint is that 30 feet from the ends is way too far. If you are rapping down looking for an anchor in the dark (etc)...yea, it would be nice to know that you have 30 feet left. But this is enough to notice and then forget about as you keep going down/looking.

Similarly, if lowering someone, 30 feet is still enough rope out that you can't tell if there is enough rope to get them to the ground.

Emergency stop, don't do anything else (do not pass go).

The 30 foot marker would be good for warning your leader that there is 30 feet left in which to find a good anchor.

^^speaking of dental floss, and mammut supersafe ropes, was that the one with some thread pulled through the rope at the midpoint? The pic i saw showed approx. an inch of thread sticking out from each side, making the middle easy to find and impossible to move. I'll have to try that with a needle and thread when my mid-mark becomes impossible to find.

http://www.rockclimbing.com/...p.cgi?Detailed=68531

A variation of the old jerry-rig trick of stitching a piece of thread through your sheath (which is not recommended by manufacturers), this method of marking Metolius’ Monster Ropes is nothing more than a day-glo piece of thread sewn through the rope itself. According to Metolius, it doesn’t compromise strength at all, but still provides a highly-visible and tactile (for ultra-spooky night rappels) warning that the end of the rope is near. Every Monster Rope being made now has this mark at the middle and 10 meters from both ends. Of course, neither Metolius nor I advocate NOT continuing to tie knots in the ends of your rappel ropes.

Of course, neither Metolius nor I advocate NOT continuing to tie knots in the ends of your rappel ropes.

if forgetting that you're near the end of the rope when there's all of 30 feet left is a problem when you rappell, then perhaps this sport isn't for you.

Emergency stop, don't do anything else (do not pass go).

i could see a use for something like this (perhaps with enough rope left to tie a mule, etc and escape that belay, deal with issues, etc), but i'd prefer to have some extra rope to work with, i can get closer to the rock, climb up a move or two, have the climber come off a little bit higher than the deck, etc...but getting to a point whereyou can't do anything else is a little um...scary.

Climbers rap/lower partners off the end of the rope every year. Just read Accidents in North American Mountaineering.

But in any event, if 10 feet of rope isn't enough to tie yourself off (if rapping) or deal with a partner who isn't yet on the ground, then, hum, maybe this sport isn't for you. :P

Tie a granny knot.

cut the middle out and put it in your pocket, that way you will always know where it is.

Use anything but battery acid.

Plus when you get gorp caught in your teeth you can bust off a piece, floss and have some hella clean gums!