How do I "Merge Orphaned threads and/or posts into a Registered Member"?

[Knightmane]

Looks like I am the first to ask about this. I used the Search feature before making this thread. Either everyone is too scared to ask or they simply don't want to sound silly or inexperienced to ask about this subject.

Anyway...

How do I "Merge orphaned threads and/or posts from a deleted member into a newly registered member"?

Here is the situation/scenario:

"A board member who had a substantial amount of posts accidentally removes himself from the board but his posts are not removed and still exist. He rejoins the board and asks the board owner if he can have his currently orphaned threads/posts merged into his new active account so he doesn't have to recreate every thread and post he has ever made."

Is there a way to do this? And if so, what is it?

Thank you in advance for any reply.