Locking carabiner for top rope master point?

I read in a book that I needed a locking carabiner for the master point on a top rope. Is one of these ok or should I use two (opposite and opposed, of course)?

Jaren Watson wrote: 
You need a locking carabiner with a combination that has a minimum of four dials, equalized, if possible.

FOUR dials! Now that's bomber.   

Key locks are better. Those combo locks are easy to crack...

The next evolution in gym safety.

Jaren Watson wrote: I seriously hope you’re just joking, but just in case you’re being serious (hard to tell with new people online), NO, this is not safe!

You need a locking carabiner with a combination that has a minimum of four dials, equalized, if possible.

What you really need is a lock where you have to cryptographically extend the block-chain record of everyone who has locked/unlocked the lock to unlock -- then you'll know who left it unlocked causing the accident.

David Gibbs wrote:

What you really need is a lock where you have to cryptographically extend the block-chain record of everyone who has locked/unlocked the lock to unlock -- then you'll know who left it unlocked causing the accident.

Good idea,  but the problem is I can only find them for sale using bitcoin.

im pretty sure by the way this was written its a troll post. 

David Dentry wrote: I read in a book that I needed a locking carabiner for the master point on a top rope. Is one of these ok or should I use two (opposite and opposed, of course)?

  

Two are of course essential, but you won't achieve appropriate redundancy unless the combinations on each carabiner are different. 

I’ve used a molybdenum bike chain as part of an anchor setup before. It was by far the strongest part of the system, lol! 

David Dentry wrote: I read in a book that I needed a locking carabiner for the master point on a top rope. Is one of these ok or should I use two (opposite and opposed, of course)?

  

That one looks like it's only rated to 4 or 5 UIAA falls. You're gonna want one that is rated to at least like 15 falls so that you don't have to go back up and change out to a new locker while you're in the middle of TRing a pitch. 

rgold wrote:

Two are of course essential, but you won't achieve appropriate redundancy unless the combinations on each carabiner are different. 

For two redundancy you need multiple mechanisms - key and combo.  Also no single person should know all the codes.  Distribute them among all the belayers.

Colonel Mustard wrote: I’ve used a molybdenum bike chain as part of an anchor setup before. It was by far the strongest part of the system, lol! 

With these lockers and your bike chain you just have to toss in a tow strap, a cut-off seatbelt, and a Home Depot pulley and it's starting to sound like a DL top rope set up.

Your gonna get robbed!

I use this and keep my house keys safe at the same time.

Notice how this locker opens outwards.  Definitely not safe to use for climbing.  But for a key chain..

rockklimber wrote: Notice how this locker opens outwards.  Definitely not safe to use for climbing.  But for a key chain..

Yep, that's the part that makes it unsafe.

F loyd wrote:

Yep, that's the part that makes it unsafe.

It was sarcasm.  Perhaps I coulda made it more obvious.