diff --git a/CppCoreGuidelines.md b/CppCoreGuidelines.md
index c87f7e7..11b786f 100644
--- a/CppCoreGuidelines.md
+++ b/CppCoreGuidelines.md
@@ -7296,15 +7296,41 @@ Casting to a reference expresses that you intend to end up with a valid object,
 
 ##### Reason
 
-???
+The `dynamic_cast` conversion allows to test whether a pointer is pointing at a polymorphic object that has a given class in its hierarchy. Since failure to find the class merely returns a null value, it can be tested during run-time. This allows writing code that can choose alternative paths depending on the results.
+
+Contrast with [C.147](#Rh-ptr-cast), where failure is an error, and should not be used for conditional execution.
 
 ##### Example
 
-    ???
+The example below describes the `add` method of a `Shape_owner` that takes ownership of constructed `Shape` objects. The objects are also sorted into views, according to their geometric attributes.
+In this example, `Shape` does not inherit from `Geometric_attributes`. Only its subclasses do.
+
+    void add(Shape* const item)
+    {
+      // Ownership is always taken
+      owned_shapes.emplace_back(item);
+
+      // Check the Geometric_attributes and add the shape to none/one/some/all of the views
+
+      if (auto even = dynamic_cast<Even_sided*>(item))
+      {
+        view_of_evens.emplace_back(even);
+      }
+
+      if (auto trisym = dynamic_cast<Trilaterally_symmetrical*>(item))
+      {
+        view_of_trisyms.emplace_back(trisym);
+      }
+    }
+
+##### Notes
+
+A failure to find the required class will cause `dynamic_cast` to return a null value, and de-referencing a null-valued pointer will lead to undefined behavior.
+Therefore the result of the `dynamic_cast` should always be treated as if it may contain a null value, and tested.
 
 ##### Enforcement
 
-???
+* (Complex) Unless there is a null test on the result of a `dynamic_cast` of a pointer type, warn upon dereference of the pointer.
 
 ### <a name="Rh-smart"></a>C.149: Use `unique_ptr` or `shared_ptr` to avoid forgetting to `delete` objects created using `new`