Common Shift Times are the shifts you use regularly and can help you create other shifts more quickly while building your Schedule. Specifically, they are the shift times you've used in the past 3 weeks, and are the ones you’ll most likely use again.
Follow the steps below to see how Common Shift Times work:
Using the 'List' or 'List by Role' layout
As you manually add shifts to the schedule while in the 'List' or 'List by Role' layout, they are auto-created for those Roles as Common Shift Times for easy re-use in future schedules.
Since they are auto-created, the Common Shift Times will appear in a drop-down menu (shown below), allowing you to quickly select a shift time.
Using the 'Time Frames' layout
While in the 'Time Frames' layout, Common Shifts Times will appear to the left, allowing you to schedule employees to fill in a specific shift.
You can add a new 'Time Frame' by clicking the 'Create Time frames' button below the existing shift times. 
BD = Business Decline
If you select BD when creating a shift, it lets the employee know they are scheduled to work with no specific end time—their shift will run until they are sent home. You may enter an estimated end time for more accurate labor-cost projections, but note that the end time you enter is NOT visible to employees.
CL = Close
If you select Close when creating a shift, it lets the employee know they are scheduled to work the closing shift.
You can edit your Close times under your Location Settings.