Is it pronounced as one-by-one or as one-to-one when read out?
Please note that this use is related to the binding structure of textiles.
Here is an example of usage from Role of Yarn Tension in Weaving by Samir Kumar Neogi (©2016):
It is observed that when the weave is changed from 4 / 1 satin to 1 / 4 satin， the average warp tensions at shedding and beaten-up increase (Fig. 7 ．38A ）