How to define the surface (???.surf) for surface_docking?

Dear Rosetta Team,

When docking a protein with a solid surface, Rosetta will need a .surf file; Any one can tell me how to setup/edit a .surf file for a certain solid surface (a .pdb file) for surface docking? In the demo example for the calcite.surf, there is not detailed instruction to tell how to do it? Only three lines, with likely X,y,z in the calcite.surf file. I dont know what they are representing for a solid surface?

Thanks

An Pu