Stretched Assignments 
The duration of stretched assignments is either exactly as long as or shorter than the time difference between the beginning and end of the assignment. Unlike capacitive assignments, the duration of the assignment conforms to the availability of the employee. If an employee begins an assignment at 8:00, for example, has a doctor's appointment from 10:00 to 11:00 (and is therefore not available), then finishes the assignment at 12:00, the system can display this in the planning row as a stretched assignment from 8:00 to 12:00, with an actual duration of three hours.
Prerequisites
In Customizing under
Sources of Demand 
Allow Stretched Assignments, 
you have defined for which order types and plants the system uses stretched assignments.The assignment that you create fulfills this condition from Customizing.
Features
If the system creates a stretched assignment, it first determines the start and end or duration of the assignment (as is the case with concrete assignments).
To determine the end of the stretched assignment, the system checks when the employee is available. The assignment therefore stretches over times at which the employee is absent (weekend, holiday, or other time allocations such as vacation or sickness), without the system considering these times in the duration of the assignment.
Note
Other existing assignments do not affect the availability of the employee. If an assignment already exists in parallel to the stretched assignment, the system displays this as a collision (see Displaying Collisions in the Planning Board).