"PolyTool" is a program which you can use to edit the polygons that Twistory uses. Its main purpose is to create polygons for historical "sphere of influence" records. Information like the name and dates of an empire are in the .ttt files. But the polygons themselves are in separate text files, and are referred to by filename inside a <file> field of a sphere-of-influence item in a .ttt file.
The first kind is PolyTool's own document type:
This type of file contains a list of polygons, and its creator is PolyTool, so that when you double-click on it in the Finder, PolyTool opens. (Since it is typed after the Mac idiom, there is no need for a filename extension.) Once you open such a file, you can create and edit polygons on the surface of the earth.
The second kind is the single-polygon file. Here is its icon:
This is a normal text file, and it contains only one polygon. This is the format in which a polygon is exported from PolyTool, and imported into Twistory. It has the default creator, SimpleText, so a file extension (.poly) is typically added to remind you of what type it is. To re-open it in PolyTool once it is exported as a text file, you have to use the "Open..." command in PolyTool.
To select a polygon, click on it. The selected polygon appears in green, and its vertices have small handles. The commands in the "Polygon" menu operate on the selected polygon. The selected vertex has an open handle.
To create a new polygon, command-click on the map where you want it. You will see a minimal polygon (open, with only two points) appear. To move a vertex, drag its handle with the mouse. To create a new vertex between two existing one, drag the smaller handle at the middle of the line segment; a new vertex will appear. To close the polygon, choose "Close" from the "Polygon" menu. To delete a point, select it by clicking on it, and then hit the delete key.
I have not bothered to give the format of polygon files here, since there is no need to use it if you have PolyTool. But it is not complicated, as a look at PolyTool's output will show. Latitude is in minutes north of the equator, and longitude is in minutes east of the prime meridian. A line beginning with "m" indicates a move to absolute coordinates; other vertices are relative.