Before personal computers, EDA, and automated tools, engineers originally used rubylith, a red plastic film sold by art-supply houses that is still used today by sign makers and graphic artists. Early chip designers would cut strips of rubylith with X-acto knives and tape them to large transparent sheets hanging on their wall. Each layer of silicon or aluminum in the final chip required its own separate sheet, covered with a criss-crossing pattern of taped-on stripes.
By laying two or more of these transparent sheets atop one another and lining them up carefully, you could check to make sure that the rubylith from one touched the rubylith from another at exactly the right points. Or, you'd make sure the tape strips