Lemme AXE you a question

While I don't really have a use for an axe living in the city there is no point in owning a dull tool. A coworker and former lumberman taught me a trick today on how to sharpen an axe or other impact edge.

Hold a file handle end above the edge and angled so the cutting teeth are perpendicular to the edge. Slide the file along maintaining a proper edge angle, do not move the file up and down. I quickly tried this today with my very dull axe and fuck me if it didn't put a damn sharp edge on it real quick.

Perhaps this is common knowledge for people who use them all the time but it was new to me and rather effective.
Let's start with what file cut you were using, please...