a way to rig multipe decoys in deep water without having to have each line long enough to reach the bottom and without having a wt on each decoy.......quicker to put out, quicker to pick up, less wt to carry.....downside is that they tend to look a little "quack quack waddlish" since they end up in pretty much straight lines.....
There's a bunch of different techniques...some people remove and attach each decoy with each deployment...some leave them attached all the time, carefully storing them in either individual pocket bags or in bins and bins, either rigid or collapsable.......
Requires a ground line...usually 100' to 150'....a wt sufficient for the size of decoys and the current in your area...a dropper on your decoys, (3' seems to be pretty standard with some using less and some more-length will depend to an extent on dog and the type of motor you run....essentially you want the dropper long enough for a dog, (if you use one), to swim over and for a prop to clear the ground line so that you can motor through the rig).....and a clip on the end of the dropper to attach the decoy to the main line......plus whatever storage setup that you use...
Personally I'm a "on and off" with each rig person....store my 100' main lines in a 7 gallon bucket....stack my big decoys on the floor and the smaller ones are in individual pocketed bags.....run the BIG clips we have been talking about because I like a bigger dropper than most....102# tarred net line..easier on the hands and on the dog.....BIG, as in twice the wt that most people say they are using, lead pyramids on both ends of the line....(13 Cork Brant in a 12' tidal swings causes ALOT of drag and anything less than that will drag)....
I regualrly hunt in from 15 to 20' of water and with that rig and a good setter can get 12 to 13 decoys on a line and put out (7) lines in about 30 minutes....picks up in about the same time after the first couple of times.....way faster than individuals in the same depth of water....
Thats the "short" version....like I said there are lots of different ideas on the way it should be done...they all work for the person using them or they likely would have switched to a different way long ago.....
Steve