Initial set-up. Red is on defense, and is called D# in this explanation. D1 is mark, D2 is big scary (preventing the inside-out throw), D3 is off-point, D4 is mid-mid. Force is to the right (flick). Force could be the other way though.
If the offense (O4 or O5) crash the cup, D7 needs to communicate, and D4 goes with the crasher. IMPORTANT - D2 and D3 stay put. D4 is playing man defense on the crasher.
Reset
If the disc is thrown to the break side, the wall must prevent...
...the upfield throw! That would be very bad.
Reset
Mark is broken. But the wall is on the way! Note: D1 runs a straight line between the handlers so that they cannot throw immediately back.
Success! The wall gets there first and prevents the upfield throw.
The mark then sets flat and the wall moves over to clog the middle. D3 (off-point) can even move up a step to prevent the cross-field throw and put pressure on the throw to O2. D5 defends against overhead throws.
Reset
If the disc is swung to the force side, D2 calls "TRAP!". When trap is called, D1 stays on handler O2, playing man defense when (s)he is in the middle of the field. D4 backs up a few steps and plays the middle of the field. D6 (the wing defender) should watch out for O5 along the line, and D7 (the deep defender) should pinch toward the sideline.
D2 (the BIG SCARY) puts a hard trap mark on (allowing only directly forward and directly backward). D3 (off point) is preventing the inside-out. D6 is preventing the upline, and should watch for offensive players in the lane. D5 is defending against the big cross-field swing or hammer (they have a HUGE space to cover!).
If handler O2 goes behind, defense D1 should NOT follow and stay in the middle of the field. Let the throw go! However, D1 should watch out for the cross-field swing.
Re-establish the trap.
If the mid handler strikes, D1 must communicate to D3 ("STRIKE!") and D4. D4 should pinch in to help stop the inside out throw. D1 stays in the dump space and prevents the cross-field dump.