diff --git a/editor b/editor
index 03c502e..8ccb1cd 100755
--- a/editor
+++ b/editor
@@ -7,6 +7,21 @@
 # Simon Tatham makes this program available under the CC0 Public
 # Domain Dedication.
 
+'''Interactive glyph editor for Bedstead.
+
+Uses Python/Tk to display a window with a pixel grid on the left side,
+where the user can click or drag to toggle pixels on and off, and on
+the right, shows the output of the Bedstead smoothing algorithm
+applied to that grid of pixels.
+
+This is done by running the `bedstead` executable itself to compute
+the smoothed outline, so a copy of that executable is required to use
+this editor.
+
+'''
+
+import argparse
+import os
 import re
 import sys
 import string
@@ -20,7 +35,9 @@ XSIZE, YSIZE = 5, 9
 LEFT, TOP = 100, 700 # for transforming coordinates returned from bedstead
 
 class EditorGui:
-    def __init__(self):
+    def __init__(self, bedstead):
+        self.bedstead = bedstead
+
         self.tkroot = Tk()
 
         self.canvas = Canvas(self.tkroot,
@@ -75,7 +92,7 @@ class EditorGui:
         self.polygons = []
 
         data = subprocess.check_output(
-            ["./bedstead"] + list(map(str, self.bitmap)))
+            [self.bedstead] + list(map(str, self.bitmap)))
         paths = []
         path = None
         for line in data.splitlines():
@@ -191,7 +208,20 @@ class EditorGui:
         mainloop()
 
 def main():
-    editor = EditorGui()
+    # By default, assume that the user ran 'make' in the bedstead
+    # source directory, so that the 'bedstead' executable is alongside
+    # the binary.
+    default_executable_path = os.path.join(
+        os.path.dirname(os.path.abspath(__file__)), "bedstead")
+
+    parser = argparse.ArgumentParser(
+        description=__doc__,
+        formatter_class=argparse.RawDescriptionHelpFormatter)
+    parser.add_argument("--bedstead", default=default_executable_path,
+                        help="Location of the 'bedstead' executable.")
+    args = parser.parse_args()
+
+    editor = EditorGui(args.bedstead)
     editor.run()
 
 if __name__ == '__main__':