go to lcsupply.com they have the traps on there for 39 bucks and if you do not want to buy one just look at the one they have on there it might give you a good idea of what to build.also i do not know how your friends barn is built but i have heard at night you can use a flashlight and fishing net to catch them while they are roosting. i also need to get pigeon but i first need ti find a place to trap them. matthew