Skis How do you adjust Silvretta 400 - need a special wrench?

I got these from ebay, and the two bindings are not adjusted the same. I've tinkered but can't see how to loosen the clamps that hold the binding at the detents.

I found a scan of a 400 Instructions for Mounting and Use that refers to an adjustment wrench, which I don't have. Don't even know what it would look like...
 
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