[3] Fold point A to the right so that a triangular flap is created. Line XY should intersect the triangular flap at a point 1/3 the length of the flap. Figure 4 shows how the model should look after step 3 has been completed.

[4] This is how the model should look after step 3 has been completed. Line BA represents the length of the triangular flap created in step 3. Note that line XY intersects the triangular flap at a point 1/3 the length of the flap.