also: split zone · sift · sift block · split flow
Inside zone with one player crossing the formation against the flow to block the backside edge. The crossing block is the sift. It is the only thing that makes the play split.
2 meanings, all below. Jump to the one you heard.
Inside zone with one addition: an H-back, tight end or fullback crosses the formation against the direction of the line's movement and blocks the backside edge defender.
What it solves is the backside end, who on plain inside zone is either unblocked, read, or chasing the play down from behind. Blocking him lets the back cut all the way back, which turns a one-cut play into one with a genuine second option. It puts a body on the exact defender who ruins zone runs.
split flowinside zone, zone readThe sift is the block. A player crosses the formation moving opposite to the line and takes the backside edge defender, usually on the move and usually from an angle that defender is not set up for.
Holding the two together is the point. "Split zone" names a play and "sift" names the one thing in it that is not plain inside zone, so a coach who knows the sift understands the play, and a coach who knows only the play name has learned nothing transferable.
sift blockwham block, veer release