You can make 4 different four-sided shapes: a kite, a rectangle, and two different parallelograms. The book shows three of them.
Remember, each piece is the same right-angled triangle. Call its sides the short side, the long side and the slanting side. Two pieces can be joined along any pair of matching sides, and the second piece can be placed either as a mirror or turned half a turn.
| Join along | Second piece placed as | Shape you get |
|---|---|---|
| slanting side | a mirror | Kite |
| slanting side | turned half a turn | Rectangle |
| short side | turned half a turn | Parallelogram (long one) |
| long side | turned half a turn | Parallelogram (flatter one) |