Gerber help sought

Prompted by my latest project (a cable pinout sensor - just plug a cable into it and you get the pinout), I want to look into the possibility of having one-off PC boards made. Everyone seems to want Gerbers, but without documenting exactly what they are. I found a PDF describing "RS-274X", which appears to be most of it, but there are lots of conventions it doesn't describe. I've found indications that there exists some open-source software, but extracting documentation from code is a mess. I'm going to be asking various people whose addresses I've found in various places. But you people are documentation packrats, so I'm asking here as well: anyone have any such doc? /~\ The ASCII der Mouse \ / Ribbon Campaign X Against HTML mouse at rodents.montreal.qc.ca / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B