So the UPS man brought me a 40LPI file and the server is down at work, so slide serrations it is. This one made my palms sweat. I could not figure out how to use a guide to keep everything straight, so I ended up with a piece of bar stock clamped to the bottom of the slide to get the first lines started and then eyeballed it from there. I expected to be able to do the entire back all at once, but you don't realize how much curve there is there until you start filing on it. I ended up doing one side at a time. It is ever so slightly not straight on the right side, but you go cross eyed trying to pick it out, so I am hoping it disappears once I PVD it.
A blue dry erase marker works pretty good as dykem in a pinch