diff --git a/FL/Fl_Copy_Surface.H b/FL/Fl_Copy_Surface.H
index fa1e96ac2..fa95f18cc 100644
--- a/FL/Fl_Copy_Surface.H
+++ b/FL/Fl_Copy_Surface.H
@@ -66,6 +66,11 @@ public:
 };
 
 
+/** A base class describing the interface between FLTK and draw-to-clipboard operations.
+ This class is only for internal use by the FLTK library.
+ A supported platform should implement the virtual methods of this class
+ in order to support drawing to the clipboard through class Fl_Copy_Surface.
+ */
 class Fl_Copy_Surface_Driver : public Fl_Widget_Surface {
   friend class Fl_Copy_Surface;
 protected:
diff --git a/FL/Fl_Image_Surface.H b/FL/Fl_Image_Surface.H
index 227a05b6a..f46e6dd3d 100644
--- a/FL/Fl_Image_Surface.H
+++ b/FL/Fl_Image_Surface.H
@@ -33,10 +33,9 @@
  draw widgets (using Fl_Image_Surface::draw()) or to use any of the 
  \ref fl_drawings or the \ref fl_attributes. Finally, call image() on the object
  to obtain a newly allocated Fl_RGB_Image object.
- 
  Fl_GL_Window objects can be drawn in the image as well.
  
- \example
+ Usage example:
  \code
  // this is the widget that you want to draw into an image
  Fl_Widget *g = ...;
@@ -89,6 +88,11 @@ public:
 };
 
 
+/** A base class describing the interface between FLTK and draw-to-image operations.
+ This class is only for internal use by the FLTK library.
+ A supported platform should implement the virtual methods of this class
+ in order to support drawing to an Fl_RGB_Image through class Fl_Image_Surface.
+ */
 class Fl_Image_Surface_Driver : public Fl_Widget_Surface {
   friend class Fl_Image_Surface;
 protected:
diff --git a/FL/Fl_Native_File_Chooser.H b/FL/Fl_Native_File_Chooser.H
index a5fd01f43..4a9221573 100644
--- a/FL/Fl_Native_File_Chooser.H
+++ b/FL/Fl_Native_File_Chooser.H
@@ -167,7 +167,12 @@ public:
   int show() ;
   };
 
-
+/** Represents the interface between FLTK and a native file chooser.
+ This class is only for internal use by the FLTK library.
+ A platform that wants to provide a native file chooser implements all virtual methods
+ of this class. Each platform supported by FLTK must also implement the constructor of the
+ Fl_Native_File_Chooser class.
+ */
 class Fl_Native_File_Chooser_Driver {
 protected:
   static void chrcat(char *s, char c);
@@ -199,6 +204,17 @@ public:
   virtual int show()  {return 1;}
 };
 
+/** A cross-platform implementation of Fl_Native_File_Chooser_Driver.
+ This implementation uses a Fl_File_Chooser object as file chooser.
+ 
+ Any platform can support the Fl_Native_File_Chooser class by implementing
+ its constructor as follows:
+ \code
+ Fl_Native_File_Chooser::Fl_Native_File_Chooser(int type) {
+   platform_fnfc = new Fl_Native_File_Chooser_FLTK_Driver(type);
+ }
+\endcode
+ */
 class Fl_Native_File_Chooser_FLTK_Driver : public Fl_Native_File_Chooser_Driver {
 private:
   void errmsg(const char *msg);
diff --git a/FL/Fl_Screen_Driver.H b/FL/Fl_Screen_Driver.H
index a96857bd1..8e041b25f 100644
--- a/FL/Fl_Screen_Driver.H
+++ b/FL/Fl_Screen_Driver.H
@@ -41,7 +41,10 @@ class Fl_RGB_Image;
 class Fl_Group;
 class Fl_Input;
 
-
+/** A base class describing the interface between FLTK and screen-related operations.
+This class is only for internal use by the FLTK library.
+Each supported platform implements several of the virtual methods of this class.
+*/
 class FL_EXPORT Fl_Screen_Driver {
 
 protected:
diff --git a/FL/Fl_System_Driver.H b/FL/Fl_System_Driver.H
index 4a6b4e2fc..8f5a8c5cb 100644
--- a/FL/Fl_System_Driver.H
+++ b/FL/Fl_System_Driver.H
@@ -40,6 +40,8 @@ class Fl_Widget;
 
 /**
  \brief A base class for platform-specific system operations.
+ This class is only for internal use by the FLTK library.
+ Each supported platform implements several of the virtual methods of this class.
   */
 class FL_EXPORT Fl_System_Driver {
   friend class Fl;
diff --git a/FL/Fl_Window_Driver.H b/FL/Fl_Window_Driver.H
index 8ed7f0664..8d1775e84 100644
--- a/FL/Fl_Window_Driver.H
+++ b/FL/Fl_Window_Driver.H
@@ -37,6 +37,8 @@ class Fl_RGB_Image;
 
 /**
  \brief A base class for platform specific window handling code.
+ This class is only for internal use by the FLTK library.
+ Each supported platform implements several of the virtual methods of this class.
   */
 class FL_EXPORT Fl_Window_Driver
 {