Plnfss is a set of macros to provide easy font access (somewhat
similar to NFSS but with some limitations) with Plain TeX.
Plnfss can automatically make use of PSNFSS fd files, i.e.,
when an Adobe Type 1 is used the relevant fd file will be
loaded automatically. For cmr-like fonts (ec, vnr, csr or plr
fonts), a special format called pfd (plain fd) is required and
must be loaded manually. See ot1cmr.pfd for further
information.

Homepage:
https://ctan.org/pkg/plnfss
