The REVO is a tube-style device with a backup-locking mechanism. In its primary function the REVO is used like a tube-style belay device where the belayer is responsible for maintaining control of the rope; feeding out and taking in slack, and catching a falling climber by pulling the rope tight against the device. While standard belay technique is required the REVO has the added security of the innovative backup-locking function. The function ensures that if the belayer loses control of the rope when a climber falls, i.e. there is excess slack in the system, the REVO will lock and block the rope. This happens when rope passes through the device at a velocity greater than 4 meters / second, roughly 10cm of slack. This function is automatic and cannot accidentally be overridden. The clever combination of these features makes this the safest belay device on the market.