[Groff] Help with crop marks code

[Walter Alejandro Iglesias]

Hello all,

Searching for how implement crop marks with groff I've found this:

http://article.gmane.org/gmane.comp.printing.groff.general/7804

That do the job but I am a bit lost with the code.  I couldn't find
documentation on internet to understand it and be able to modify it to fit the
A4 paper format I use.

I would appreciate some clue or a point to some documentation.


Thanks in advace.


        Walter