Definition
A vertical stack is an offensive formation where the non-active offensive players (typically four to five) line up in a single vertical line through the centre of the field, in front of the disc. The stack is positioned to leave clear cutting lanes on the open and break sides — cutters peel off the back of the stack to attack one of those two lanes.
In Context
Vertical stack is one of the two main shapes in our system; the other is the Spread Stack. We use vert when we want a clear single-cutter picture — one player attacks at a time from the back of the stack, with the rest of the stack acting as space and as the next-cutter queue.
The defensive choice we are creating with vert is binary: cover the cutter or leave the cutter free. Because the lanes are clearly defined, poaching from the stack is also clearly visible — and punishable.
Vert is where most of our handler Give-and-Go work happens, because the stack does not interfere with the central handler space. See Vert Stack - Handler Flow and Continue and Vert Stack - Breakside Under for the dedicated drills.