Organization of observed targets in plate designs and on physical plates, using the field 180+04 as an example. This field has 12 anticipated visits, which are covered by four designs (indicated by blue, yellow, green, and orange). Each design has stars from one of four short cohorts (S1, S2, S3, S4), one of two medium cohorts (M1, M2), and the long cohort (L); that is, stars in the long cohort appear in all four designs, and stars from the medium cohorts appear in two designs. At least one plate is drilled for each design, and some designs (here, the first two) are drilled on multiple plates. Most frequently, this occurs when a field is to be observed at different hour angles (HAs), as in this example. Figure from Zasowski et al. 2013, their figure 1.