Flagging Eiders - How to rig

[Joel]

I watched a video of people flagging eiders. It seemed very interesting. The majority of my wider hunting is out in boat with decoys set. That said I'd love to give flagging from shore a try. I'm interested in knowing how to rig the flags. Do they have to be cut a certain shape or are they store bought? Whlat height does the pole have to be to be effective? How is the clothesline placed?