I know that the Herculis is 'null and void' BUT, for me. it remains a challenge to complete this xword.
So, I find this discussion interesting -
I googled and the first response entries cam up with references to CORF - then I confirmed this google result to several dictionaries -->
http://www.onelook.com/?w=corf&ls=a
I did not look further, but after Jim Jools came up with CORB, I have found this also -----
Similar references in The Online Plain Text Dictionary and The Webster 1913 Dictionary which actually refer to BOTH Corb and Corf in the same line!
http://www.mso.anu.edu.au/~ralph/OPTED/
http://humanities.uchicago.edu/orgs/ARTFL/form s_unrest/webster.form.html
In Both these dictionaries -
Corb .... a basket used in coalmines
Corf .... a large basket used in carrying or hoisting coal or ore
So, I think that CORF is the better answer?