These simple devices have a number of uses. Predominantly designed to reduce cannibalism in pheasant flocks, they have a number of additional uses with domestic poultry. They work on the simple principal that you can’t peck what you can’t see. The simple device clips to the nostrils using a central pin that anchors it firmly in place. Unlike similar products, no tools are required and there is no risk of ‘hook up’ injuries with this model. It is ideal for control of feather picking and I have had success using them for reducing rooster aggression. In the latter, the bird is less inclined to attack if it cannot target properly so attacks are  often misguided and overall attacks are reduced. Initial placement can be a little daunting. With this style, due to the wide wings, the peepers can be custom fitted to each rooster if needed. The inside edges of the peeper can be trimmed to accommodate comb variations without affecting the function. Once you have the shape right, I find placing the pin through the first peeper hole before fitting is easier than trying to line up everything at once. Insert the pin into the nostril, push through the fine septum and back out the other nostril and into the second retaining hole in the peeper. Peepers can be removed if circumstances change by simply snipping off the barbed end of the pin.