You can close any item you belong to, even if you didn't create it. Closing an item prevents people from adding new messages to it and removes it from item lists.
To close an item:
Open the item.
Click , then click Close <Object>
Optionally, enter a summary statement.
Click Close.
To reopen an item:
From the navigation menu on the left, select the type of object you want to reopen.
In the Show menu, select Closed.
Click an item to open it.
Click , then select Reopen <Object>.
To discard an item:
You can discard an item only if you're the sole member. A discarded item is removed from all lists, including collections and Social Objects it's related to.
Open the item.
If necessary, remove all other members except yourself.
Click , then select Discard <Object>.