Against teams that play H-stack. We will often run a Sag-D. The mark is always straight up. When the disc is in the center of the field, the defenders on the side handlers (1&3) will sneak into the lane positioning themselves so they are slightly upfield and can see BOTH their man and the disc.
When the disc swings to the sideline, the defender now on the mark (3) must seal all upfield throws. The other handler defenders will sag off.
When the handler with the disc looks back at the dump (2), the defender (2) should bite
and return
When it returns middle (2), the defense goes back to its coverage
Should one of the handlers push up field, the mark(2) should shade back to the other handler while the other handler defender (1) works a sag with them.