Blocker is the ability to stop the simultaneous creation and add some consistency creation to process workflow. So, adding a blocker stops a process from running at a given point. No issue after that point can be created until the tasks before aren't completed. This simple action turns basic runs into powerful Process workflows.
You can use a single blocker in your workflows, add a series of blockers to the specific sections of your process, or add blockers to every process step, which effectively enforces the order in which your workflow run is completed.
Blocker can be used to Steps and Approval.
Instruction on how to add Step Blocker
Select the Step or Approval to which you want to add the blocker
Click the Add blocker button and confirm your choice. When the block is added, a flag icon will appear next to the step, for easy understanding of which tasks are blocked.
Step Blocker - the system will not start following Steps until the Blocked Step is completed (Form has been submitted).
Approval Blocker - the system won't start following Steps until all Approvals make a decision.
Save the Template, so all new Processes started will support the recently added Blocker. As soon as the form that contains the block is submitted, all other tasks will be created at once (to the next Block if such is available).