Hey Dalthamion, if you've sold the item, you can mark it SOLD & lock the thread so that people can't keep asking if it's sold or not!
All you need do is to click on edit in your first post in the thread, then click on advanced when the edit screen comes up. Once you are in the advanced edit screen, find the drop down list alongside Prefix, and change the prefix from FS to SOLD. Then save the changes & the thread prefix will now say it's sold & no-one but a Mod or Admin can post in the thread either.
(SOLD) For Sale RS ST Comfort Seat
