I recently wrote a post giving a very simple explanation of the outside zone and zone runs in general. One popular variant that I did not discuss was the “pin and pull” zone. The Indianapolis Colts use this variant quite a bit, as did the Minnesota Gophers back when they had Lawrence Maroney and Marion Barber under Glen Mason. This is a staple of the one-back, two-tight end offenses that the Colts use and was famously used by Elliott Uzelac as offensive coordinator for the Colorado Buffaloes in the early 1990s.
Here is a basic explanation. Generally, one way to think of it is that uncovered linemen pull; alternatively uncovered linemen “block back” to get a good angle and the covered linemen pull. Just depends how you teach it. Here are some sample rules:
The aiming point for the Single Back is one yard outside of the tight-end.
If the Center can reach the Nose he will make a “you” call to the strongside guard telling him to pull and block the middle (“Mike”) linebacker. The strongside tackle and tight-end will “tex” — i.e. an exchange: the tight-end blocks down while the tackle wraps around. The tight-end down blocks to prevent penetration; the tackle pulls and runs to reach the strongside (“Sam”) linebacker.
If the center cannot reach the nose he will make a “me” call to the strong guard telling him to block the nose and the center will pull to block the “Mike.” The strongside guard blocks down and to disallow the noseguard from penetrating. The strong tackle and tight-end will “Tex” as described above.
Below is a video of Penn State using what was, apparently, the pin and pull zone. (Courtesy of mgoblog.)
(Note that I could be wrong on identifying this as an example of “pin and pull,” as it could be a simple down or “G” scheme. Though the idea gets across.)