Push in/ pull out the office ruller by one hand. Designed for plastic office rulers, expected ruler thickness is 2.0 to ~4.4mm. Slim version can take 2.0 to ~3.6mm. It may hold also other object of this thickness (e.g. SD card).

Use double-sided adhesive tape to place the holder (clip) where you wish. Can hold ruler in any direction. Use 2 holders for long ruler.

Print with 3 perimeters, 0% infill, 0.4mm nozzle. Optionally you may try 0.6mm nozzle (not tested). PETG recommended, PLA could be ok too.