Index: trunk/Ohana/src/opihi/cmd.data/mslice.c
===================================================================
--- trunk/Ohana/src/opihi/cmd.data/mslice.c	(revision 40334)
+++ trunk/Ohana/src/opihi/cmd.data/mslice.c	(revision 42128)
@@ -31,4 +31,5 @@
   if (argc != 4) {
     gprint (GP_ERR, "USAGE: mslice <input> <output> plane [-x,-y,-z]\n");
+    gprint (GP_ERR, "  extract 2D image from 3D cube (opposite of mlayer)\n");
     gprint (GP_ERR, "  -z is default\n");
     return (FALSE);