The Shunt is great, but there are some potentially dangerous gotchas in its operation. Never use it with ropes of different diameter. As a rappel backup, the sh

The Shunt is great, but there are some potentially dangerous gotchas in its operation. Never use it with ropes of different diameter. As a rappel backup, the shunt can fail if you place it above your belay device. The risk is that a panicked operator will hold the device open. In the correct mode of operation, you place the shunt below your belay device. If you're disabled, the shunt will lock off. If you panic and hold it open, the force you apply to the device will arrest your rappel.