The ladder is depth turned vertical: a fixed price column centered on the mid, with resting bid and ask size on each side. It is the panel futures traders live in.
One price axis
Resting size, the last trade, and your working orders line up on a single price column, where you act. The ladder reads the same normalized book as the montage and the heatmap, so all three agree.
Built for click-to-trade
The ladder is the intended home for click-to-trade order entry, which arrives with the execution engine. Placing, moving, and cancelling orders directly on the price axis is the point of a DOM, and the panel is laid out for it.
What is coming
Click-to-trade wiring and a live equity depth feed are the next steps for this panel.