Heard an anecdote relayed from Oklahoma State's offensive coordinator (good coach, entertaining speaker). He was talking about the four verticals concept, which I and Dan Gonzalez recently explored in depth.
As Dan explained, the key to this whole concept is the "seam-reader" -- the slot receiver who reads the deep coverage and can run a post, seam, or square-in. And as I explained, even if you don't give that player a full panoply of options, at minimum you tell one slot guy to read middle of the field open (two deep safeties) or closed (one deep): against middle of the field open the guy splits the safeties to streak down the middle void; against middle of the field closed the receiver stays up the hash to put the free safety in a bind between the two slot players.
In Okie State's terminology, they call this player the "beater." One thing Dan and I didn't talk much about was how do you decide which guy you want to be the "beater" or "divide route" -- the "get open" guy.
The first diagram shows it with the slot:
And the second shows it with the tight-end here (it could also just be the other slot):
So how do you choose who you want running it? Typically, as Dan draws it up, he likes his best receiver to line up in the slot and to drill that down. You also can do it just to the field: if the ball is on one hashmark you can have the receiver to the wide side run it because he has more freedom.
Brewer addressed this question, and talked about that for him it is often a matter of personnel. Specifically, if you get in three-wide gun (as Okie State often is), the defense often subs in a nickel defensive back for a linebacker. But the problem there is that the defensive back is better than the linebacker: he doesn't go for all the fakes and moves that the seam-reader or "beater" player uses to get open.
To illustrate what they did he told an interesting anecdote. Brewer used to be an assistant and offensive coordinator at Marshall back in the Bob Pruett days, where he coached Chad Pennington (and some guy named Randy Moss). They decided to run the "beater" to the side where the linebacker was and away from the nickel back.
But the problem was that the other teams would often shift this. Fortunately, Pennington was a pretty bright guy, so they let him determine who was going to be the beater pre-snap.
And how did they communicate it? Pennington would get to the line, turn to the side where the linebacker was and not the nickel defender (and hence the also the slot he wanted to run the "beater"), and would just clap in that general direction. Everyone knew what it meant, and off they went.