You can ensure a service is left unfilled by checking the "Leave this service unfilled (don't auto-schedule) setting in the Edit Service dialog in the Schedule Skeleton.
- Open the Schedule Skeleton and select the service you wish to leave unfilled.
- Click the Edit Service button.
- In the dialog box that appears, click the setting that says "Leave this service unfilled (don't auto-schedule).
When you Commence Scheduling, MSP will leave the service unfilled. You can then manually schedule these positions later or post them to the Web Terminal to allow volunteers to sign-up online.