Avoid using Blocked columns on Kanban Boards

One of the common anti-patterns that I often see with Kanban board design is the use of a Blocked column. Although I mentioned it in an earlier post on blockers, I think this could do with additional highlighting because I continue to see this when I start with teams. Using a Blocked column seems fairly simple at first, but it ends up taking away a lot of important feedback and actions. Using a blocked column often leads to confusion in the workflow, unpredictability, longer lead times and the lack of leadership emergence.

What not to do

As you can see from the diagram above, there is a basic process and at the end of it is a blocked column. When something is blocked people move that ticket to the blocked column. Herein begins the problems that I will describe in turn.

  • No action on blockers – usually when blocked items are moved out of the flow they become “out of sight, out of mind”. That is, they tend to be forgotten about and no immediate action occurs. This is especially the case if people aren’t walking the board from right to left in their standups / kanban meetings.
  • Long lead times – when blocked items don’t get actioned, the lead times for those items begin to blow out. Oftentimes, the tail of your lead time histogram probably has many extended lead times due to inaction on blockers (see Lead Time Distribution Charts).
  • Unpredictability – the lengthening of the tail of your lead times will result in a less predictable system of work. This will start to impact your customers and will make it harder for you to manage delivery and expectations. When the blocked column doesn’t have a WiP limit this is further exacerbated as essentially your overall system is no longer WiP limited, thus inherently unpredictable.
  • Where does it go when unblocked? – this question often arises since the item has been blocked for so long, we forget which step in the workflow the item got blocked in. If you do remember where it goes, you’ll likely run into the WiP limits exceeded problem below as well. There are other reasons why cards shouldn’t move backwards on a kanban board.
  • WiP Limits exceeded – this happens in two parts.
    • Firstly, when something is blocked and moved to the blocked column, often someone starts a new item – increasing the total WiP in the system. Since there is usually no WiP limit on the blocked column, WiP in the system can increase dramatically and rapidly with this approach.
    • Secondly, when an item becomes unblocked the question is what to do with it. If it gets moved back into the position it was in within the flow, it will most likely exceed the WiP limit.
  • Metrics will be out – things like your CFD chart are going to be out as a result of moving things backwards and forwards in the flow.
  • Lack of leadership emergence – we want to achieve “leadership at all levels”, so we really need leadership to come from the team / service group around blockers. We should be seeing a “let’s do something about it” attitude about blockers – with managers and team members actioning the underlying causes. However, with a blocked column, there is no real call to action and little leadership tends to emerge. This will hold back the groups maturity over time.

Instead, try this

Block items in place. Put a blocker sticky (for physical boards) on the item and record the following:

  • The item blocked (eg ID)
  • The start and end date of the blockage
  • The symptom / cause of the blockage

The above data will become important later on as it will allow you to do blocker clustering.

When using an electronic board, make sure that you choose one that has the capability to flag blockers in place and record the metrics for later analysis. Here is an example board:

Story 5 is blocked by Defect 1, Story 4 is blocked because it’s waiting on something from another team.

Ideally, the tool should also give you some basic information you can use for blocker clustering to action the problems. However, not many tools actually do this, so you may need to find another way to extract the data for analysis & action. Here is an example tool:

Using this alternative, will often have the opposite effect of what we saw above, including:

  • Action of blockers
  • Leadership emergence
  • Stability of system and metrics
  • Clarity of process and limits on WiP

Conclusion

You should avoid using a blocker column on your Kanban board design. There really are no positive effects from using it and plenty of negative ones. Blockers are impediments to good flow and should be called out and actioned as a priority so please take some time to reconsider how your board is designed and think about a better design option for blockers.

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