gs...a demand feeder is one that has a plastic rod(about 1-1/2' long) sticking out the bottom of feeder.When the deer or what ever can reach it,touch it ,it moves and more corn falls out.You can build your own using a plastic bucket(with a lid of course)'cut a 2 " hole in bottom and place a stick shaped like a old wooden sling-shot like I'm sure you craved out as a kid.Of course I'm lazy so I bought mine at Wally World for about 18 bucks a piece.You can spend about 10 bucks more and get the dust/dawn feeders or a little more and get feeders with timers. The only thing I see wrong with my feeders is they should have been 7 gal not 6 gal.Reason,you can't fit 50# of corn in 6,but you could 7. Rick