How to delete messages I've sent to someone on Facebook?

[Travis]

Someone on Facebook had upset me and I blocked them. I saved our conversation to reference back to what they had written in a message. After a couple of weeks I opened the messages between this blocked person and I and noticed that somehow they had deleted their sent messages to me, I can only see a small blank icon for each message they sent to me. But all my sent messages are still there. I'd like to know how this person was able to do that?

[SPYDERBLADE]

When you blocked them, they became invisible to you. This includes their messages. You are invisible to them, including your messages. If you want to delete your messages, click on the delete option.

[Santhoshkanth]

It's Simple when you follow my steps.. 1.go to your inbox and select which conversation you want to delete. 2. then there is right top of the conversation the action button available 3.then you simply click the button it shows some pop menu then make click on delete messages then you select some specific message to delete.. By these way only they delete their sent message