The instructor:

- Asks children to study figure A.
- Points at the word "Diagonal" and tells children "diagonal" means reaching from angle to angle.
- Tells children a diagonal divides a rectangle into two right triangles.
- Asks children to look at figure B.
- Tells children that two diagonals divide a horizontal or vertical rectangle into two acute and two obtuse triangles.
- Asks children to look at figure C.
- Tells children that two diagonals divide a square rectangle into four right triangles.
- Tells children the center is where the two diagonals cross.

The instructor:

- Asks children to the name the shapes of parts 1 and 2."
- Asks children to the name the shapes of part 3."
- Asks children to the name the shapes of part 4."
- Asks children to the name the shapes of part 5."
- Asks children to point to the center of the square rectangle.
- Asks children to point to the center of the horizontal rectangle.

Children complete the following drill work:

- Draw a horizontal rectangle and divide it into two right triangles.
- Draw a vertical rectangle and divide it into two right triangles.
- Draw a square rectangle and divide it into two right triangles.
- Draw a square rectangle and divide it into four right triangles.
- Draw a horizontal rectangle and divide it into two acute triangles and two obtuse triangles

The instructor:

- Asks children to study the bottom image.
- Tells children this drawing contains sixteen large rectangles and fourteen large triangles.
- Asks children to find and trace the rectangles in the picture with their forefinger.

The instructor asks children the following about the bottom image:

- Where is an acute triangle?
- Where is an obtuse triangle?
- Where is a right triangle?
- What is the shape of the stone work of the bridge?
- What is the shape of the bank on the right? The bank and its reflection together?
- What is the shape of the stone abutment and the bank together?
- What is the shape of the stone abutment and its reflection?
- What is the shape of the bank and its reflection?
- What is the shape of the truss?
- What is the shape of the beam?
- What is the shape of the space under the beam?
- What is the shape of the whole drawing?
- What is the shape of the space above the roadway?
- What is the shape of the whole space below the roadway?