This may be it..............he puts a slight bevel on front dog to reduce travel distant clip must pry dog up. Tapping on top of the clip with a hammer does the same thing to raise the bottom of the notch to remove all travel. Dog will sit firmly in and on the notch.......and right on the edge of letting go. Probably trap size and use specific. A 330 set for beaver or otter in water probably needs to be less sensitive than a smaller trap set for smaller animals.

http://www.trapperman.com/trapperman/Basic_Sets_Bodygrip_Adj.html