So the polypeptide is linear and they're basically stacked on top of one another. Now, just like in the helical case, where we have two different types of alpha helixes, we have the right handed and the left handed. We also have two types of beta pleated sheets. So we can have these two linear peptides or polypeptide chains basically point in the opposite directions or they can point in the same direction. So anti parallel directionality basically means they are stacked on top of one another, but they point in opposite directions. And the parallel data sheet basically means they're stacked on top of one another and they point in the same direction.