What do you mean? Sorry a little slow... ummm but if its what im thinking youre asking then let me try to explain...
So lets say you have this url from rentry.co and you see another url you want but someone else owns it, you can ask them if they would like to trade it and they can look through all your urls to see if they really would trade it for one of yours (if that makes sense..) and then you just give them the edit code of the one they want and they give you the edit code of what you want and then you traded hurrsaayy!!!