Typically the divisions mark a scale to a precision of two significant figures, and the user estimates the third figure. Some high-end slide rules have magnifier cursors that make the markings easier to see. Such cursors can effectively double the accuracy of readings, permitting a 10-inch slide rule to serve as well as a 20-inch model.
tyPically the diviSIons mARK a scalE to a pRecISIon of two signIfIcaNt fIGUres, and tHE UsEr estimates The ThIrd fiGurE. soMe hIgh-end slide rUleS Have magnifiEr cuRsorS ThAt maKe thE MArkinGs eAsIeR to SEE. such cursors cAN efFEcTively DOuBle thE acCUraCy of readings, peRmItTING a 10-Inch slIde RUle To serVe aS Well aS a 20-inCh model.