As I am getting back into trapping again, I took my Trapper Ed course today. After the amount of hours I have spent on this site -- I already knew most everything that was taught today - except: The instructor carries empty sand bags back in for beaver sets. They weigh almost nothing, and can be stuffed in your back pocket. He uses on-site rocks or mud to fill them, wires them shut, attaches the drowner cable and tosses them in the water. When pulling sets, he just empties the "stuff" out and re-uses the bag again. They cost about 75 cents each and last forever.