[curtain]

0.004" is read as "four thou", and 0.0005" as "five tenths", as in five tenths of a thou, FWIW.

I only picked up imperial thanks to binging This Old Tony videos.

[sokoloff]

If you enjoy https://www.youtube.com/c/ThisOldTony, you might also enjoy https://www.youtube.com/c/Clough42 https://www.youtube.com/c/Blondihacks and https://www.youtube.com/user/JohnGrimsmo

[mNovak]

Unless it's PCB, in which case its "4 mil", as in milliinches, among the great bastardized units