Small modification but i do it to all mine.

Trap jaws generally come with a slightly rounded edge & inner surface. This is great for land trapping canines, etc.
But for better holding power on beaver do this -

SQUARE off the lower inner part of jaws & the contact faces of jaws. You can do this with a metal file without dismantling trap.
Getting the inner jaws & contact faces good & SQUARED off creates a better grip & hold on a beavers foot.
Less chance of a pull out especially if it's a toes catch.

Again you only want to do this on your beaver/otter drowning set-ups. NOT on your land animal traps