The AFM files output by screenafm should be placed in the directory of the font itself.
For more information about how to create and install fonts, see the document Preparing Fonts, available on-line in /NextLibrary/Documentation/NextDev/Concepts.
When screenafm is run, it looks for the AFM file for the given font in the current directory, in the directory ../afm, and then in the three standard AFM file directories (see below). The inclusion of ../afm is often helpful when working in a conventional font source tree.
/NextLibrary/Fonts/ location of NeXT-provided fonts
/LocalLibrary/Fonts/ location of local fonts
~/Library/Fonts/ location of user fonts
Obsolete directories still searched by screenafm:
/NextLibrary/Fonts/{outline, bitmap, afm} location of NeXT-provided fonts
/LocalLibrary/Fonts/{outline, bitmap, afm} location of local fonts
~/Library/Fonts/{outline, bitmap, afm} location of user fonts
screenafm shouldn't look in ../afm or the afm subdirectory of the standard font directories, since they're not supposed to be used anymore.