U need dogs with a bit of leg under them but narrow chested which i find very hard to comeby thats the size sorted then u need one that is willing to crawl down a crack in the rocks head first some times quit a number of feet .then the best i find are the one that tackle and bay which flusters the fox sometimes forceing him to bolt or move sometimes to a worse place in the rocks to be able to dig or sometimes better a baying dog which some times people think r needed r not the best cause charlie will be happy to stay there all day bad news in awkward spot when u dig to dogs in rocks they r in