Old name cards

What do you do with the old name cards when you've changed job or been promoted?

I use it as rough papers to jot things down, on the back of the name card of course. If your name card is 2 sided, then obviously this won't work. If it's one sided, it works very well as rough papers~ Because it's heavy and it won't fly away like other small papers. It's best for me to write down 4D numbers... HAHAHAHA......