hi prof,

i want to make a pointer to point the user's attention to the upper scale number like the way for the bottom scale.

like in the lower scale
i changed to (xp , y2-size) for the arrow for the bottom

so for example,

12.5 mm = 12 + 0.5 mm

need to understand how you reference the coordinates of 12 in the drawing panel?
chance to explain?  ;D

there is an website applet that i am trying to customize to do