Braided Paper "pleat sink" ?

[fncll]

Can anyone explain to me what a "pleat sink" is? I am talking about step 8 of this diagram for Nolan's Braided Paper model: http://www.origami.cz/Pdf/braided.pdf

Sara Adams has posted a video for this model but she uses a different sequence and I'd really like to be able to figure this pleat sink thing out...

[Raptorex55]

I believe this is just another term for open sink. I've never seen it used that way, but I believe it is referring to how you should have alternating mountain valley folds.

[Brimstone]

It is called pleat, because it is not just one sink, you have to go mountain, valley, mountain, valley like when you fold an accordion, a fan or a pleat.