Autofold

Faces must remain planar at all times in SketchUp. Therefore, SketchUp will Autofold, or

score, faces as necessary to accommodate any operation that will result in warped faces.

In the left-most image above, a six-sided polygon volume's top face (created with the

Polygon Tool followed by the Push/Pull Tool) was rotated using Rotate Tool. Because of
SketchUp's sticky nature, the sides of the shape, which share common edges with the top

face, twisted and folded with the rotate operation (right-most image).

What you are not seeing is that SketchUp has created hidden geometry when performing
this Autofold operation. The following image shows the 3 dimensional shape with the hidden

geometry shown (dotted lines). Notice that each twisted faces are actually comprised of two

triangular faces.