HELP-Sliders on a ruler

Hello,

I need some help with this slider. I need the slider to move precisely at 2/16, 4/16, 6/16 and 8/16 on a ruler. I have all of the states for a rectangle to move with the slider but I cannot figure out how to get the slider to move precisely where I want it. 

I also want allow the user to input equivalent fraction numbers into the empty boxes. Can you please assist me before I pull out my hair? Thank you