Index: action_details.html
===================================================================
--- action_details.html	(revision 31737)
+++ action_details.html	(revision 31738)
@@ -2687,7 +2687,7 @@
 </ul>
  
 <p>
- A polygon is a pcb layer object, that is: if it's fullpoly, it may have multiple islands. The result is zero or more polygon layer objects, each with a single island, created on the current layer. 
+ A polygon is a pcb layer object, that is: if it's fullpoly, it may have multiple islands. The code operates on the clipped shape of the input polygons, not on the 'as drawn shape'. The result is zero or more polygon layer objects, each with a single island, created on the current layer. 
 <p>
  The rest of the arguments will build a flat list of polygon objects to work on and need to address at least two polygons. Each argument may be one of: 
 <ul>
@@ -2721,7 +2721,13 @@
 </i>
  to address polygons, if multiple polygons are selected or found at the time, the order they end up added to the operation object list is undefined. 
 <p>
- Input polygons are unchanged, new polygons are created on the current layer.  
+ Input polygons are unchanged, new polygons are created on the current layer. 
+<p>
+ Demo video: 
+<a href="https://archive.org/details/polybool">
+ PolyBool(sub) mini-howto.
+</a>
+  
 </dd></dl>
 
 <h2 id="polycombine">PolyCombine</h2>
Index: action_reference.html
===================================================================
--- action_reference.html	(revision 31737)
+++ action_reference.html	(revision 31738)
@@ -13,7 +13,7 @@
 <table border=1>
 <caption>
  <b>
-This is pcb-rnd 2.2.1 (svn r31696) an interactive printed circuit board editor ,  Revision: 31736
+This is pcb-rnd 2.2.1 (svn r31696) an interactive printed circuit board editor ,  Revision: 31737
 </b>
 <th> Action <th> Description <th> Syntax <th> Plugin
 <tr><td>About</td><td>Present the about box</td><td>About()</td><td>dialogs plugin</td>
Index: action_src/polybool.html
===================================================================
--- action_src/polybool.html	(nonexistent)
+++ action_src/polybool.html	(revision 31738)
@@ -0,0 +1,31 @@
+The boolean operation argument is one of these:
+<ul>
+	<li> unite: calculate the union of the polygons
+	<li> isect: calculate the intersection of all polygons; the result is the area where all argument polygons are present
+	<li> sub: subtract subsequent polygons from the first polygon
+</ul>
+<p>
+A polygon is a pcb layer object, that is: if it's fullpoly, it may have
+multiple islands. The code operates on the clipped shape of the input polygons,
+not on the 'as drawn shape'. The result is zero or more polygon layer objects,
+each with a single island, created on the current layer.
+<p>
+The rest of the arguments will build a flat list of polygon objects to
+work on and need to address at least two polygons. Each argument may be
+one of:
+<ul>
+	<li> object: the user needs to click an object using the GUI
+	<li> selected: all selected polygons are appended to the list
+	<li> found: all found (green highlight) polygons are appended to the list
+	<li> <i>ipdath</i>: address a specific polygon
+</ul>
+<p>
+Note: for the <i>sub</i> operation the first polygon is special, so order
+of attributes matter. When using <i>selected</i> or <i>found</i> to address
+polygons, if multiple polygons are selected or found at the time, the order
+they end up added to the operation object list is undefined.
+<p>
+Input polygons are unchanged, new polygons are created on the current layer.
+<p>
+Demo video: <a href="https://archive.org/details/polybool"> PolyBool(sub) mini-howto.</a>
+