A Gantt milestone is a significant event
...
in a project schedule represented by a marker on a Gantt chart. It indicates the completion of a major task or deliverable and serves as a visual representation of the project's progress.
Milestones typically have a specific deadline and represent key points in the project timeline. In ProScheduler WBS Gantt chart, milestones are usually depicted as diamonds with 1 day duration placed on the timeline to indicate the completion of a major task or objective.
...
...
Create a new milestone
A milestone can be created in the same way you plan a task, just need to mark it as a milestone. A milestone has duration of 1 day and start date is always equal to the end date.
Convert a task to milestone
Open the menu on the Gantt bar and click
...
Convert to milestone
Convert a milestone back to a task
...
by opening menu on the diamond and click Convert to task