the scale of a ruler, but it is divided up in 0.5 mm marks with every seventh tick mark a bit longer than the rest (like you would do on a metric ruler for every 0.5 cm), and every 14th tick mark even longer (like you would do for 1 cm), and the longest tick marks are numbered in multiples of 7 mm
https://assets.chaos.social/media_attachments/files/113/183/565/765/269/445/original/2244670d02a94888.png