We have the same style of feeder that Yay Chicks! has, that's pictured in the link. They come in a couple of different sizes. It works well to keep chickens from billing out their feed, which is where they sweep the feed out of the feed tray with their beaks.
chickens wasting feed - Page 2
- CluckN'Crow Farm
With our flock the only time that they did this is when Tractor Supply stopped carrying Kent feed and only carried Purina. Since Purina was all that they had I bought it and my chickens were not having it. They billed it out of the feeder apparently in search of the food they were used to. This when on for about 2 months and I was at wits end with all of the food waste and extra cleaning I had to do not to mention all of the dust in the coop, so I went out seeking a place to buy the Kent 16% layer crumbles that they were used to. Finally found a place to buy it and at the very moment I filled their feeders with it ALL food wasteing immediately stopped!