On the Sawtooth in normal mode, these twoThere's a male buckle that slides along the strap running underneath the pack. The photos on MR's website show that male buckle attached to the female buckle you're asking about when the load shelf is not in use (and detached when the load shelf is in use). I don't see what that buckle set actually accomplishes though. On my Sawtooth it doesn't seem to make any difference whether it's attached or detached.
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