I was just sent a Build file with instructions on how it would solve some problems I’ve been having with a module I’m building. Problem is I have no idea what a Build File is, how to use it, or how to open it. But Vassal doesn’t recognize it, at least mine doesn’t and I’ve got the latest version of Vassal.
A buildfile is an XML document. You will need a text editor to view it. It is normal and expected that VASSAL will not open it directly, as it is simply one of the internal prerequisites of a valid module file.
VASSAL modules are simply zip archives with a different file extension. The absolute bare minimum required elements of a valid module are a buildfile (what you are really modifying when you use the VASSAL editor) and an images directory. There can be other elements, such as predefined setups (saved game files) or HTML documentation. These items all get bundled into a zip archive–again, with a .vmod suffix instead of a .zip suffix–to form a module.
So if I change the vmod to zip and open it as a zip file, I can then extract the build file that’s there and then insert the new one into the zip file?
I would strongly encourage the use of 7zip, which is an archiving utility that will happily open anything it can without the need to change file suffixes. It will save you a lot of time to open your .vmod directly with it and extract/insert files as needed.