Hey, not really directly related to rat or beaver huts, but similar concept for late winter predator sets though. My uncle actually was first one to point this out to me, and I've worked on the concept enough years now to believe the extra effort is well worth it.
In this corner of the state, coon are the bread and butter of the industry, and pocket sets work well for them (as well as for most other water critters in the location). When the creek freezes up we noticed a lot of coyote and fox tracks using the creek (frozen, or if a shallow or dry creek then the snow in the bottom of it) as a mini protected travel route. We also noticed that every old coon pocket we had along that creek would be worked by coyotes and foxes traveling the creek bottom. Those old pockets still smelled like fish, fish oil, lure, etc. So I started working on sets to reactivate the old pockets into just big horizontal dirtholes, so to speak. I use sandwhich baggies under the trap in a shallow chopped out bed in front of the hole. If it is ice in front of the hole, then a hole is chopped and the trap secured to a length of stout brach and this is inserted into the hole and then turned sideways under the ice so that it cannot be worked back up through the same hole. Center the chain in center of the log, too. If it is a dry creek bed, then I just pound in an earth anchor stake system.
I pick up a lot more fox than coyotes in this set, but I think that in this area fox like to stay low when traveling and the coyotes seem to stay more out in open. I do get quite a few coyotes in them, though.
Have to really watch your weather so that if things warm up or creeks rise that you get your traps back in ahead of time.
Anyway, its just something that I wanted to pass along to everyone.