Provides a means for defining the overlay performance of microlithographic stepping exposure systems used to expose resist- coated FPD display substrates ("FPD steppers"). FPD substrates may contain a single-layer in which separate sections are created by multiple reticles, unlike the patterns that are produced on semiconductor wafers by a single reticle. Defines the parameters necessary for specifying overlay performance of FPD steppers, for both single- and multiple-reticle applications. Does not cover quality differences between different reticles used for the qualification of the tools. These differences must be quantified for validation of the statistical derivation of performance measurements against this specification.