Block leading - don’t “trap” the leader
When block leading, the same person leads several pitches in a row. (As opposed to swinging leads, when you alternate leads with your partner.)
Consider this anchor scenario (left photo): The leader arrives at the belay, and clips themselves directly to the master point carabiner (purple) with a clove hitch. Then, they put their second on belay with a Grigri, which is also clipped to the master point carabiner.
This is fine for swinging leads, but . . .
Can you see the (small) problem here when block leading?
How can you prevent the issue by rigging slightly differently?
Whoops, how is the leader going to remove that clove hitch without deconstructing most of the anchor? They can’t. (Ask me how I know this is a problem; I’ve done it!)
By cloving directly to the master carabiner, the leader has essentially “trapped” themselves. Even if they did clove themselves on the gate side instead of the spine side, they would still have to open the masterpoint carabiner, which is less than ideal.
When using a master point carabiner like this, it's good to think of it as being ‘“welded” closed; once it's shut, it doesn't get opened again until the anchor is completely broken down.
(Admittedly, this is a minor mistake and not a lethal one, but it’s annoying and usually takes a few unnecessary shenanigans to decluster it.)
A better rigging choice is shown on the right.
Here, the leader uses one extra locker to clove to the master carabiner. This allows them to easily unclip and continue to lead, without being trapped in the system, and without opening the master carabiner.
In most cases, clipping in like this with one extra locker is usually a better choice, because it gives you more options for general rigging and declustering unexpected situations.
For example, when you agreed to swing leads, but your partner arrives at the anchor and says “Hey, how about you keep on going, I’m tired . . .”
Other concerns, issues?
I know there are some anchor Polizei who are gonna get their feathers ruffled because the second is not belayed next to the spine of the carabiner. IMHO, it's nothing to worry about. The largest possible load when bringing up your second is going to be 2-3 kN; no possible way the carabiner could be damaged from that.
Concerned about three-way loading on the carabiner? It's fine. Carabiners loaded like this have been tested to break at about 17 kN, WAY more then you're ever gonna put on it and a recreational climbing context. Check out the photo below from Black Diamond.
