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.