[texhax] TFM file format

[Karl Berry]

    Is this documented, I'd like to find the width information for font
    characters, I found the document :
    https://www.tug.org/TUGboat/tb02-1/tb02fuchstfm.pdf It seems to have
    contradiction, first the header is lh words long (2), then it
    describes 18 word header.

The header is variable length.  lh is that length.

Incidentally, I suggest looking at tex.web or tftopl.web for the tfm
definition.  I don't think any actual changes were made after that
article, but the exposition, at least, became more polished.

Happy hacking,
Karl