You have a box which is more than large enough to contain the object.
You have several locks with keys.
The box has a locking ring which is more than large enough to have a lock attached.
But your friend does not have the key to any lock that you have.
Note that you cannot send a key in an unlocked box, since it might be copied.
How is this done?
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Attach a lock to the ring. Send it to her.She attaches her own lock and sends it back.
You remove your lock and send it back to her.
She removes her lock.