The Printer Font Metrics (PFM) file generator creates PFM files whenever the installer locates downloadable font files, but fails to locate a FINSTALL.DIR file. The installer assumes it will have to build PFM files from the downloadable font files. It reads the header from the font file plus the widths of each individual character and uses that information to build the PFM file.
Please notice that when the installer scans a disk for fonts and there is no FINSTALL.DIR file, it will ignore any PFM files already on the disk and will attempt to generate PFM files from the font files. It will also recognize cartridge PCM files.
It is highly recommended that font manufacturers provide their own PFM files because vendor-supplied PFM files will more accurately represent the font than PFM files generated by the PFM file generator.