I have racoon problems. I have seen them pull off chicken wire stapled to 2x4s. I need to install an automatic chicken door, and I know how to do that using a slide style door. The problem is that the openers and doors have no 'lock' mechanism. They all rely on gravity to close the door. Has anyone had problems with raccoons opening a sliding door like this? Seems to me they would easily be able to lift it and get inside. I know the door is supposed to slide past a ledge so they can't get their fingers under to lift, but sometimes shavings will get under it and prevent that. Can a coon open a sliding door? I would add weight, but the openers are only rated to 4 lbs.