diff --git a/src/AccessControl/ZopeGuards.py b/src/AccessControl/ZopeGuards.py
index e1d4166..73515f6 100644
--- a/src/AccessControl/ZopeGuards.py
+++ b/src/AccessControl/ZopeGuards.py
@@ -275,6 +275,12 @@ def __next__(self):
     next = __next__
 
 
+# The following three view classes are used only for mappings of type `dict`
+# (not subclasses). Therefore, the mapping does not have security assertions
+# and cannot acquire ones. As a consequence, the `guard` calls used in their
+# methods verify that the checked key or value is accessible based solely on
+# its own virtues, i.e. either because it is public or has its own security
+# assertions allowing access.
 class _SafeMappingView:
     __allow_access_to_unprotected_subobjects__ = 1