The UNR-Rohn Rohn-Loc is basically an open-sided Type 1 Lever Cam Ascender. The safety is interesting. There are two spring-loaded pins (one is visible at the top of the rope slot), one of which keeps the rope in the slot at the top, and the other keeps the cam from opening far enough to free the rope. These are set up so that the cam can be locked in the open position (using the hole visible in the cam lever), yielding a more compact package when not in use.
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©2007, Gary D. Storrick