Step 1

set up. endzone. vert stack. in the middle. from the back of the endzone

Step 2

handler calls "redline" and a cutter who has "crabs" (aka they're way faster than they're defender) goes to the back of the stack (in this case it's #4)

Step 3

#4 (from the back of the stack) cuts immediately to the open side

Step 4

if it fails, then normal vert stack continues