Side Closure cards - how?

[tashast]

I keep seeing those neat side closures for cards. I would love to be able to figure out the measurements but when I do a search for side closure, I end up with a bunch of stuff that doesn't relate. Can anyone help me? Here is a link to a card that uses it.
Thanks much!!

Gallery at Splitcoaststampers

[longtimestamper]

this one has directions:
Gallery at Splitcoaststampers

[craftymom]

looks like a match book card to me. they have just decorated the bottom flap and turned it on the side.

if that is the case, take a 3.5 x 12 piece of paper. hold it at at 5 inches. Then fold up the extra piece to make the flap.