WIP Limits for Lanes
It is possible to set WIP (work-in-progress) Limits for vertical and horizontal lanes, so that you get a visual feedback when this limit is met or exceeded. To set WIP Limits for lanes, go to Set up view → Limits:

The example above shows the limit for In Dev set to 5. Now the exceeded WIP Limit is explicitly
seen on the view, which will alarm you and your team whenever the limit is exceeded by pulling too
much work into progress..