Members and sponsors now have the ability to close or re-open their own posts in the buy and sell sections.
To close a thread, go into the thread, select Administrative. Close thread will be the only option. Select proceed. This will close the thread (lock it).

Close.jpg

To re-open a thread that you have closed, go into the thread, select Administrative. Open thread will be the only option. Select proceed. This will open the thread (unlock it)

Open.jpg

Any issues, please don't hesitate to contact a mod/admin for help.