Point 17 (5t-l 7) :
This point is located at the centre of the nipple.

Point 18 (5t-21) :
Move four thumb-widths above the navel. Now move two
thumb-widths either to the right or the left. This is point 18.

Point 19 (5t-29):
Move four thumb-widths below the navel. Now move
two thumb-widths either to the right or the left. This is point
19.