diff --git a/README.md b/README.md
index 402a9e4..047625e 100644
--- a/README.md
+++ b/README.md
@@ -39,7 +39,8 @@ This comprises four components, links to docs below:
  industry standard font file to Python source. See below.
  2. [Writer and CWriter classes](./writer/WRITER.md) These facilitate rendering
  text to a monochrome or colour display having a suitable device driver.
- 3. [Creating icon fonts](./icon_fonts/README.md)
+ 3. [Creating icon fonts](./icon_fonts/README.md) Ways to incorporate icons in
+ a Python font file.
  4. [Device driver notes](./writer/DRIVERS.md). Notes for authors of display
  device drivers. Provides details of the font file format and information on
  ensuring comptibility with the `Writer` classes.
diff --git a/icon_fonts/README.md b/icon_fonts/README.md
index 15130c2..c93e753 100644
--- a/icon_fonts/README.md
+++ b/icon_fonts/README.md
@@ -3,8 +3,10 @@
 It is possible to display icons by incorporating their images in a font file.
 There are `.ttf` and `.otf` files available which can be converted to Python
 using `font_to_py.py`. I have not had much success with these. I also wanted
-to create my own icons. I also experimented with using a font editor to modify
-an existing font. I found the font editor unintuitive and hard to use.
+to create my own icons. I experimented with using a font editor to modify an
+existing font. I found the font editor unintuitive and hard to use. However it
+does have the advantage of producing scalable fonts which can mix normal glyphs
+with icons.
 
 The solution offered here uses the Linux `bitmap` editor plus a utility to
 convert a set of its output files to a Python font file. The image below shows
@@ -14,7 +16,7 @@ typical usage.
 
 # The bitmap editor
 
-This is documented in the man pages, but it is easy and intuitive to use. To
+This is documented in the man pages. It is easy and intuitive to use. To
 generate (say) 19x19 icons, issue
 ```bash
 $ bitmap -size 19x19
@@ -23,19 +25,24 @@ Save each bitmap under a different name: I use a `.c` extension as they are C
 source files.
 
 You need to create an additional icon to provide the output under error
-conditions, i.e. if an attempt is made to display a glyph not in the font.
+conditions, i.e. if an attempt is made to display a glyph not in the font. All
+icons in a font file must be the same height.
 
 # The file list
 
 Create a text file listing the bitmap filenames, one filename per line. The
 icon to be used as the default (error) image should be first. Subsequent icons
-will be assigned to characters "A", "B", "C"...
+will be assigned to characters "A", "B", "C" sequentially.
+
+The file list can include comments identified with `#`.
 
 # Creating the Python font
 
+This uses `c_to_python_font.py` which runs on a PC and requires Python 3.8 or
+later. The file `font_to_py.py` should be in the same directory.
+
 Assuming a file list `my_file_list.txt`, the following will create
-`my_font.py`. It requires Python 3.8 or later. The `font_to_py.py` file should
-be in the same directory.
+`my_font.py`.
 
 ```bash
 $ ./c_to_python_font.py my_file_list.txt my_font.py