2

Three lateral landmarks

Occlusal tip of the right canine, buccal cusp of the left first premolar and mesio-buccal cusp of the right first permanent molar

3

Surface + one landmark

The medial point of the right third ruga and the surface selected on the palate

4

Surface + three landmarks

The medial point of the right second palatal ruga, the medial points of the right and left third rugae, and the surface selected on the palate