In reply to Rock Badger:
As per everyone, loose for gear, tight for rope. Not only does it give a system so you can check all of your 'gear' crabs if you are a sport climber, gear being bolts in this case and bolts really wear crabs fast and can cause nicks in the crab. If this end was cipped to rope by mistake, the rope would be running through a burred carb, not good for rope! Also, floopy end going to gear is by design too. You clip a wire, hex, whatever and when the QD hangs on its own, clipped to gear and rope, sometimes it can be that the gear crab is laying gate against rock or a protusion, the theory is, should the rope come tight in a fall, the crab could be pressed against the rock and the gate pressed open. Open gate = weak crab. If the gear crab is floppy, its dead easy to rotate the crab so the gate isn't on the rock. Noticed more when clipping pegs really as you don't tend to always have a choice which way you can hook a crab on a peg.
Sorry if many know all this, it just this comes up a lot.