Data Type Yes/No (Yes/No field: A type of field with content set to either Yes or No; also known as a Boolean field or a True/False field. For example, the Recurring field indicates whether the task is a recurring task.)
Entry Type Calculated (calculated field: A field in which the value is determined by Project based on information in other fields. Project may recalculate the value automatically or when you specify, depending on your choice of calculation settings.)
Description The Summary field indicates whether a task is a summary task.
How Calculated If a task is a summary task, the Summary field contains Yes. A summary task (project summary task: A task that summarizes the duration, work, and costs of all tasks in a project. The project summary task appears at the top of the project, its ID number is 0, and it presents the project's timeline from start to finish.) is made up of subtasks and summarizes those subtasks, which appear indented under a summary task in your task list.
Best Uses Add the Summary field to a task sheet if you have multiple levels of summary tasks in your schedule and you want to be able to identify and filter for all your summary tasks. The Summary field can also be used to apply text formatting only to summary tasks.
Example You have temporarily organized your tasks in a different order than their original outline. To see which of the tasks are summary tasks, filter for and review this field.
Remarks You can apply text formatting, such as font style or color, to summary tasks only, in the Text Styles dialog box. Make sure you select Summary Tasks as the item to change. The changes you specified are applied to all summary tasks.