The "classic" moonshiner's mash barrel usually had a capacity of approximately 55 gallons, but such containers—whether wooden, plastic, or metal—either require preparation and sealing or are too expensive for most folks to bother with. Besides, that quantity could prove somewhat wasteful while your mash and alcohol production are still in the experimental stage (and prone to an occasional mistake).
So we've designed an easy-to-make fermentation kit based on a smaller container that can be had for little (or no!) money. Our "barrel" is nothing more than a slightly modified five gallon sealable bucket, the type commonly used by wholesale food distributors to supply restaurants with pickles, coleslaw, potato salad, and the like. After the eateries have emptied them, they usually throw such containers away or sell them for as little as $1 .00 apiece.
To convert your container into a mash barrel, simply drill a 1/4" hole in its lid, then get yourself a 1/4" brass pipe-to-hose adapter, and solder or braze a 1/4" flat washer to the shoulder of its threaded side. Next, cut a short length of 1/4" threaded coupling (which will serve as your nut), put a small amount of silicone sealant on the face of the washer, slip the adapter into the hole in the lid (with the hose fitting on the outside), and fasten it in place with the threaded coupling. Finally, attach a 3-foot length of 1/4" hose to the fitting on the bucket's cover.
Now you're almost set to make some mash, but before you do be certain that the barrel is clean. Wash it with a diluted bleach solution (a 10-to-1 water-to-whitener mix is fine), then rinse it thoroughly in warm tap water. After your mash mixture is sealed In the container, drop the free end of the vent hose into a jar full of water (the tube will then allow the gases from the fermentation process to bubble out but won't let any air back into the barrel).
For a more convenient arrangement, you can purchase what is called a fermentation lock (a self-contained air trap) from your local winemaking supply shop or by mail.