A hammock task is dependent on external dates for its start and finish dates and, ultimately, its duration.
The name, hammock task, is derived from the way a hammock's shape is determined by the distance between the points to which it is attached.
- Create the task to become the hammock.
- Go to the task that will drive the start date of the hammock and create a Start-to-Start relationship with the hammock.
- Go to the task whose finish will drive the completion of the hammock and create a Finish-to-Finish relationship with the hammock.
By doing this, the hammock (sumary) activity will be representative of the underlying / linked set of activities.