Black Diamond’s quality control lab tested autoblock belay device common misuses and provided extensive details. Specifically they looked at:
– incorrectly using a standard belay device as an autoblock device
– using multiple biners as the â??brake barâ? in order to make taking in rope easier
Regarding the multiple carabiner test, they found that using two biners increases the amount of force required to take rope in and increases the amount of holding force.
Check out the post for the full results.