Find close to home small stream. In the warm autumn or summer day, go with your child. On the way tell him about bamrah, about where they live, what they eat and how they build dams. Ask the kid to build a dam on the Creek, as do the beavers. In the course can take anything from pebbles, twigs, clay. The dam should not leak!
Before returning home, ask for a small Builder to parse its structure to the stream quietly flowed on, may be, to the real beavers. A dam is a spectacular sight. Most likely the kid will like this lesson, and he will want to repeat it