Index: user/06_features/hierarchic/index.html
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--- user/06_features/hierarchic/index.html	(revision 10206)
+++ user/06_features/hierarchic/index.html	(revision 10207)
@@ -327,6 +327,16 @@
 <p>
 Not yet supported. (TODO)
 
+<h4 autotoc="yes"> Expert: non-graphical sheets </h4>
+<p>
+Non-graphical sheets define object directly in the abstract model,
+they do not represent concrete model sheets. Hierarchic mechanisms (like
+connecting child sheet terminals to sheet ref sym terminals) depend on
+working with concrete model sheets. Thus non-graphical sheets can not
+participate in the hierarchy at the moment but can be used as root
+sheets in global scope.
+
+
 <h4 autotoc="yes"> Expert: spice unslotting </h4>
 <p>
 A special use case for hierarchic designs is "unslotting" a symbol