Mark as Sold is a feature for Sellers in the Buy/Sell category where you can mark your item as sold once you’ve completed your transaction with the Buyer. This will remove the listing and let users know that it’s no longer available. 

To mark the ad as sold:

1Click the Navigation Menu button. It appears as a person icon, K icon (initial icon), or your profile photo.
2From the drop-down menu, select My Ads and make a selection from the active listings menu.
3Select the Mark As Sold button next to the ad you would like to state is sold.