Sixteenths of an inch. There are sixteen of them between each mark 
    16/16 = one inch  
    Again notice that you count all of the longer marks. Each step of the way, you count the marks for that fraction and the longer marks, but not the shorter marks 
    Where is 3 15/16? [hint: 3 16/16 = 4", so 3 15/16 is 1/16 less than 4]    |