[Zope] change plain HTML file to page template?

How can I change a regular html file to be a page template? I can't see anything in properties that would allow this and have even looked at a page template file to see what's different from manage's point of view and can find nothing. Of course, I could create a page template, copy/paste, then rename, but there must be a property of some sort attached to the file, so how... Also, is it possible to create a file from an external source (FTP, etc.) so that file becomes a page template? If not, it's sure be nice to not have to go into the management interface and either create the file, download, edit, the upload or do the create/copy/paste/rename business. Thanks! --Steven