A square corner is the corner of your page or your book — that neat, straight corner. Watch these scissors as they open: first just a little, then out to a square corner, then really wide.

Which opening is bigger than a square corner, and which one is smaller?

Here is our paper right-angle tester. It fits a square corner exactly.

Watch what happens when we hold it against three different openings. Look for whether the opening is narrower than the tester, fits it exactly, or is wider than it.

Today we sort angles into three groups on the board: smaller than a right angle, a right angle, and bigger than a right angle.

We'll sort the easy ones first, then test one that is very close to a square corner.

One pupil drags on the board. Everyone else, decide the group in your head, and thumbs up when you agree.

Now sort these yourself.

The last one is very close to a square corner — test it carefully with your paper tester.