Keep your event roster full by enabling a waiting list.
Setting up a waiting list for your event allows you to have a list of users who are ready to go should there be a cancellation. You can add a waiting list to any time slot that has a maximum number of volunteers.
Multiple ways to promote or notify volunteers of an opening.
When you create a waiting list, you can choose to have users automatically promoted from the waiting list to the event when there is an opening. You may instead choose to notify all users on the waiting list for a first-come, first-served opening, or only allow an administrator to promote a user from the waiting list.
Administrators have total control.
Administrators may re-order the waiting list and choose to promote a volunteer from the waiting list to the event at any time.