I saw this set on the old T-man before the crash. It was done by Darcy Alkerton. I also saw it in Fur Fish and Game. So here we go.
I start by getting a fresh poplar pole about 3-4 inches in diameter. Cut it long enough so that it will be long enough, before you find the actual depth of the water. You will want to then cut it off so that it sticks up about 3-4 feet.
When selecting the area for it get as close to or in their feed pile as possible. You will be able to see the stems and tops sticking through the ice and snow if you have it. Chop a hole or cut it with a chainsaw about 1.5 feet wide by 2.5 feet long. This way you will be able to get the pole and snares in without knocking them off and be able to pull the beaver out later on. Push the pole that you cut through the hole until it touches the mud. Make sure it does not have a ot off stems down the hole. These will knock the snares off the pole as you lower it. Then push it in the mud a ways so that it will stand up and be solid at top and bottom when ice in the hole freezes. Pull the pull back out. You now have the water depth (from the top of the mud at the bottom to the top where the water ends. You then have to find the thicknes of the ice. Add this and another 4 inches on. This will be where the top of your snare will be. Cut a few slices of bark off the pole to make it look like the beavers have already started on it. This is one of the main attracters.
When you have the depth you will then be able to find out how many snares you need to put on. First have your safty wire (a strong cable that will run from the bottom of the pole, holding all your snares, and tie to a seperate support stick a the top so you dont lose snares or pole. Then slip/attack snares to cable. You will have 2 snaes per row. One on each side. Make the diameter of the snares 8-10 inches. You will want them 4 inches bellow the ice and 4 inches above the mud. Depending on the depth you may have one row of 2, two rows of 2, three rowes of 2, etc. Use some wire to hold your snare loops onto the pole. Make the wire wrap around the pole but not over the cable. This will prevent a beaver from knocking your other snares off the pole. On a snare pole people have caught as many beaver as there are snares.
When you have all you snares on lower the pole into the water and push into the hole you made in the mud. Get another pole to go across the hole. Tie you support wire strongly to this. This horizontal pole will be what will keep the beaver from dragging everything under.
If you want you can covver the hole with spruce bows, grass, or etc and then cover with snow. This will prevent the ice from freezing thick. When you check you wont have to chop through nere as much ice.
Only check the pole every 5-7 days. Beavers are sound shy and will not come out of their lodges for sometimes up to 3 days.
Here are some pictures of a set that would be ready to lower under the ice. (The ribbon shows where the ice would be).
Hope these plans help you
Any questions just pm me
Happy trapping.