Let's be honest: we've all seen a chicken squeeze through a gap we swore was too small. It's like they're made of liquid and pure mischief. So when a reader asks whether the door gaps on an old dog run need further securing, our answer comes from experience and a healthy dose of paranoia.
Yes, those gaps almost certainly need more wire. A determined raccoon can reach through a space you'd think only a snake could manage, and a weasel can flatten itself like a furry pancake. The chickens themselves will test every weak point, not because they want to escape, but because they're born explorers with a talent for finding trouble. If the door needs to stay functional, don't panic. You can attach a strip of hardware cloth to the inside of the door frame, cut to match the door's swing, and secure it with screws and fender washers. Use a small hinge on one side so the wire flap moves with the door. That way, the door opens normally, but the gaps stay closed.
We also have to talk about the bottom. That little wedge of space under a door is like an open invitation to every predator with a strong back and a grudge. A strip of rubber or a weighted flap of hardware cloth attached to the bottom of the door can seal that gap without ruining your hinge. It's not glamorous work, but neither is finding a pile of feathers where your favorite hen used to stand.
What this means for you, the chicken keeper who inherited a dog run and dared to dream: you are already ahead of most people by asking the question. That instinct to double-check is what keeps flocks safe. The run itself is solid, dog runs are built tough because dogs are escape artists with teeth. Now you just need to think like a predator for ten more minutes. Crawl around the door, look at it from chicken eye level, and imagine a raccoon's arm reaching through. If you can fit two fingers through a gap, a raccoon can fit four. Seal it with hardware cloth, a few screws, and a healthy dose of "better safe than sorry." Your feathered friends will thank you, probably by not disappearing, which is the highest compliment they can give.