diff --git a/Manual.md b/Manual.md
index da72bd9712..90c8dcb65f 100644
--- a/Manual.md
+++ b/Manual.md
@@ -750,6 +750,9 @@ built for, available architectures can be found under `common/cross-profiles`.
 In general, `archs` should only be set if the upstream software explicitly targets
 certain architectures or there is a compelling reason why the software should not be
 available on some supported architectures.
+Prepending pattern with tilde means disallowing build on indicated archs.
+First matching pattern is taken to allow/deny build. When no pattern matches,
+package is build if last pattern includes tilde.
 Examples:
 
 	```