Note (March 6, 2017) Version 0.0.3 has been reported broken by a change in Facebook. The upcoming version 2.1 (currently awaiting review by AMO) should fix the problem until Facebook changes things again. The following information is about the new version 2.1. Purpose Automates deleting certain posts (sold or archived) out of a Facebook group. Deleting posts

Log into Facebook and click on your group in the left navigation bar
Under the group's banner is a horizontal menu with buttons like `Discussion`, `Sale Posts`, `Members`, `Photos`, etc. Click the `Sale Posts` option.
In the new page, look just below the button your just clicked, there's a big bold `All Sale Posts` message. Look directly right of that for a gray `Recently Posted` drop down menu and click it to open it.
In the newly opened menu, click either `Sold` or `Archived` to go to your sold or archived posts feed. Note that the `Archived` option is untested and may not work (it's probably harmless, but might just break the page instead of extracting stuff like you want).
The add-on only works on posts that are currently loaded in the page. If you want to delete a lot of posts at once, you'll need to scroll a long way down the page to load them. The Page Down key on your keyboard tends to be pretty fast at this.
Once you have a a satisfactory number of posts loaded, click the add-on's button to delete them all.
The add-on will take over the current tab and start loading the links into it one by one, deleting each one in turn.

Cancelling If you accidentally start the add-on deleting the wrong posts, you can click the add-on's button again to stop it. This will close the deleter tab. Note about security This add-on is not a hack that lets you delete arbitrary posts. It just automates deleting posts you could already delete manually. That means if your friend makes an embarrassing post about you, this tool can't delete it. Not even if it's really embarrassing and you really want it gone. Contact Bugs can be logged on the add-on's bug tracker on Github or you can PM the developer (Song Taylor) on Facebook.