This step has become a LOT EASIER in recent years! There are 2 options:
1. OrbNumber: In Step 11 of this guide, you were reminded to run application OrbNumber to re-number the nodes of your finite-element grid (.feg) file for minimum bandwidth. OrbNumber now has a new feature: It always produces an extra output file with a sequential, counterclockwise list of all boundary nodes, featuring their new numbers. I like to call this a “perimeter (.per) file”. It is not yet a “boundary conditions (.bcs) file” but it is a template for creating one.
2. FiniteMap: If you use my graphical map-making code FiniteMap to produce a plot of your finite-element grid (.feg) file, you may notice that another option is to produce an “Overlay” graphical layer containing overlay type #2, which is the “outline of .feg file”. If you run this option, an extra output file is produced, which lists the boundary nodes in sequential, counterclockwise order. I like to call this a “perimeter (.per) file”. It is not yet a “boundary conditions (.bcs) file” but it is a template for creating one.