Originally Posted by WWJD
I'm thinking the 49ers use to use some type of blocking that would get their opponents all riled up. I think it was the crackback block.
WWJD...you're refering to what is known as the "legwhip". The 49ers were notorious for it in the mid-80s to the early 90s. Basically an O-line guy will "take a dive" so to speak, ie. faking that he's been pushed off his feet by the opposing player and as he is going down he whips his leg around behind him trying to connect is foot with the other guys knee.
I remember guys being interviewed about it like Howie Long and Reggie White and how they felt it was way way over the line and endangered guys careers. Sometime in the early 90s it became illegal and you could get an Unsportsman Like Conduct call if you got caught at it.