This beaver trapping technique has been around for a long time, and for good reason. There are few more effective ways to attract beavers toward a trap than by finding one of their telltale slides, creating a scent mound at the base of it, and topping it with a rival beaver's castor.
Beavers have castor sacs and release castoreum in combination with urine to mark their territories. This scent is strong and lingers around marshy areas where the critters are known to live, especially during breeding season in the early spring.
Once the mound is constructed, Steve and I bed the MB-750 coil trap just below the water and rig the drowning chain to a heavy plate that we place in deeper water. We also make sure it's deep enough to drown the beaver quickly once the trap is sprung.