By closing a thread, users will still be able to access all messages within the thread, but there will no longer be the option to reply to any of the thread's messages. If the thread is open, any message can be replied to.

Make sure you are already logged in. From the thread listing, if the value of the "Closed" column is "No", the thread is not closed, so you may click the link to close the thread. If the value of the "Closed" column is "Yes", then the thread is currently closed, and you may click the link to reopen the thread. Figure 1 shows the thread listing with the "Closed" column.

Closing Threads
Figure 1: Closing Threads