The Iwasaki Flat Tapered File Extra Fine is a 200 mm flat Japanese file that narrows toward the tip, with extra fine teeth.
It's handy for easing the sides of a housing (dado): the file can lie on its side in the bottom of the groove, which keeps the handle out of the way so you can work along long housings. Iwasaki's teeth are milled and chemically etched. They're curved and set out like a single cut file, and the face of each tooth is shaped like a small chipbreaker, so the shaving breaks off and lifts away instead of clogging the file. It cuts quickly like a rasp but leaves a clean surface like a file, and the waste comes off as tiny shavings rather than dust. The edges have no teeth, so you can work right up to a surface you don't want to cut.
It has 175 mm (6-7/8 in) of cutting length and tapers from 20 mm (3/4 in) wide down to 5 mm (3/16 in). It cuts on the push stroke. It works on wood, bamboo, MDF, plastics and resins.