Index: alien_formats/io_altium/model.txt
===================================================================
--- alien_formats/io_altium/model.txt	(revision 35582)
+++ alien_formats/io_altium/model.txt	(revision 35583)
@@ -1,3 +1,5 @@
 - union index: placement grouping, mainly for components
 - user routed: when explicitly false, the object is placed by the autorouter
 - fill object on plane layer is poly hole; no other drawing objects on planes
+- mech layers: there are normally 4, the format has 16; they should all be
+  boundary; protel users can set if a mech layer is copied to all layers