Turn over and rotate symbols
The turn over and rotate symbols are diagram marks that tell you either to flip the paper to show its other side or to spin it flat on the table without flipping.
Turn over is usually drawn as a looping arrow and means flip the model like the page of a book, left to right, so the back becomes the front. Rotate is drawn as a curved arrow around the model, often with a number such as 90 or 180 degrees, and means turn it while it stays face up. In animations, both are shown as smooth motions between steps.
Confusing the two is a common source of frustration, because the next step then looks impossible. After any turn or rotation, compare your paper with the next picture: the same edges, corners and flaps should be in the same places. Flip left to right rather than top to bottom unless the diagram says otherwise.