对折的

Once it's popped open, your cootie catcher will look like Picture 10.

现在把东南西北这样对折，打开上面的形。

The shape of cross-section is an ellipse folded in half through one symmetry axis, and the axis keeps perpendicular with pinacoid-view.

断面形状为沿对称轴对折的椭圆，此对称轴始终垂直轴截面，其向与平面图上的流道中线无关。