Way back before he became famous, Hafthor Bjornsson was a potential Indianapolis Colts signee. Unfortunately for the world of football, he decided to focus on strongman competitions and acting, but we can always imagine what it would be like for a man that huge to line up alongside more conventionally sized players.
Or, we could watch John Krahn, from King High in Southern California:
Krahn is listed at 7 feet tall and 440 pounds, although he is reportedly looking to shed some weight in order to improve his footwork. I can't imagine what it must feel like to try to block him. Probably not great.