Gatekeepers and Trial Horses are an important part of boxing. These underappreciated fighter serve as tests to up-and-coming young fighters; and as paydays to older fighters on their way down. Men like John Dino Denis, David Bey, Jose Roman and Joe Hipp give it their best, even if that isn't enough to earn them a title shot. Here are 20 additional heavyweights to match against each other or fighters from other sets.