Using the architectural ruler, layout the blueprint or design you want to read. On the sketch or blueprint, look for the scale. This is usually placed on the page’s bottom left-hand side. On the architectural ruler, find the corresponding scale, such as 1/4″ = 1′ (1/4 inch equals 1 foot). Align the ruler’s edge (the side with the “1/4” mark at the end) with the item to be measured. Step 5: Put a zero at the start of what you wish to measure and write it down.