This diagram is from the excellent book “Alpine Rock Climbing Handbook” by Austrian Guide Jürgen Reinmüller. Connect with Juergen on Instagram, @alpinstil.at, and get his book here (printed version in German, eBook in English). The diagram is shared here with permission.
A tragic 2026 accident in Kalymnos Greece is a reminder that even a two bolt anchor is not necessarily always reliable.
Can you trust that glue in bolt? Looking at it can only tell you so much.
For a more “kinetic” test, clip a carabiner to the bolt as shown, grab the gate side, and give it a twist to apply some extra leverage.
The bolt shouldn’t move. If it does, start looking for ways to back it up.
Don't do this with anything larger than a carabiner or you might damage an otherwise good bolt.
This works best with a glue in bolt, because it's all one continuous piece of metal. With mechanical wedge bolt, the hanger is separate from the bolt, so the twist test doesn't really tell you much.
image: from “Alpine Rock Climbing Handbook” by Jürgen Reinmüller
Here's a nice Instagram video from IFMGA Guide Jan Schneider @bergfuehrer_schneider showing how it’s done.