only in patch2:
unchanged:
--- a/chessboard.module
+++ b/chessboard.module
@@ -1,5 +1,8 @@
 <?php
 
+// Load all Field module hooks for Chessboard.
+module_load_include('inc', 'chessboard', 'chessboard.field';
+
 function chessboard_border_filename($border) {
   // $border: T, B, L, R, TL, TR, BL, BR
   switch ($border) {