I participated in a BOM quilt where it had /16 measurements. It was strongly suggested that we buy the ruler that is marked in /16 increments. I did and loved the results.
Unfortunately I am not at home so I can't tell you the ruler.
You might try www.quiltersrule.com for that ruler as they sell such a variety and are really nice folk. [they talked me out of buying a quantity of rulers and instead I bought just one and then after using it knew which rulers I really needed without busting my budget.]
ali