Usually, when a user takes out an advert it will be displayed for X amount of time, and then the advert expires. Simple and effective.
However what happens if it is a SINGLE ITEM and it has been SOLD during this time? Then item will look like it still available, when it actually isn’t!
The Mark As Sold (MAS) extension adds an extra tool of letting the advertiser mark their own adverts as ‘Sold’.
This of course is in addition to you, the administrator being able to mark it as sold!
This is a secure feature that does not require any extra user privileges or role, as once activated it is effectively part of your website’s core code.