diff --git a/mps/manual/source/index.rst b/mps/manual/source/index.rst
index 3d6247d8427..14de69f5865 100644
--- a/mps/manual/source/index.rst
+++ b/mps/manual/source/index.rst
@@ -11,6 +11,7 @@ Memory Pool System
     guide/index
     topic/index
     pool/index
+    topic/porting
 
 
 Appendices
diff --git a/mps/manual/source/todo.rst b/mps/manual/source/todo.rst
index fa0f983dd54..31eae295070 100644
--- a/mps/manual/source/todo.rst
+++ b/mps/manual/source/todo.rst
@@ -87,22 +87,24 @@ Outstanding
      :c:func:`mps_arena_collect`, :c:func:`mps_arena_start_collect`,
      or :c:func:`mps_arena_step`?
 
-106. :c:func:`mps_arena_unsafe_expose_protection` and
+107. :c:func:`mps_arena_unsafe_expose_remember_protection` and
      :c:func:`mps_arena_unsafe_restore_protection` are kind of hairy
      (as well as having absurd names). What's the use case? Exposing
      the MPS "is expected only to be useful for debugging" so why have
      special unsafe functions for optimizing the expose/restore
      procedure? Maybe these should be left undocumented?
 
-107. Have I correctly explained why the documentation is not very
+108. Have I correctly explained why the documentation is not very
      forthcoming about the set of result codes a function might
      return?
 
-108. NB's `MPS Format Protocol
-     <http://info.ravenbrook.com/project/mps/doc/2002-06-18/obsolete-mminfo/mmdoc/protocol/mps/format/index.html>`
+109. NB's `MPS Format Protocol
+     <http://info.ravenbrook.com/project/mps/doc/2002-06-18/obsolete-mminfo/mmdoc/protocol/mps/format/index.html>`_
      says that formats A and B are deprecated. Surely this isn't the
      case? That would leave only auto_header supported.
 
+110. Say something about assertions in the error chapter.
+
 
 Complete
 --------
diff --git a/mps/manual/source/topic/index.rst b/mps/manual/source/topic/index.rst
index 71373fb7389..154c6b8e667 100644
--- a/mps/manual/source/topic/index.rst
+++ b/mps/manual/source/topic/index.rst
@@ -18,8 +18,6 @@ Reference
     cache
     pattern
     finalization
-    plinth
-    platform
     telemetry
     message
     debugging
diff --git a/mps/manual/source/topic/interface.rst b/mps/manual/source/topic/interface.rst
index 76cb7bc9387..cebdb68447b 100644
--- a/mps/manual/source/topic/interface.rst
+++ b/mps/manual/source/topic/interface.rst
@@ -1,12 +1,12 @@
 .. _topic-interface:
 
 
-Memory Pool System interface conventions
-========================================
+Interface conventions
+=====================
 
-This document describes the C programming language interface
-conventions used by the MPS. It also contains our :ref:`policy for
-support for the public identifiers <topic-interface-support>` and
+This document describes the conventions used in the programming
+interface to the Memory Pool System. It also contains our :ref:`policy
+for support for the public identifiers <topic-interface-support>` and
 :ref:`definitions of general types <topic-interface-general>` that
 appear throughout the interface.
 
diff --git a/mps/manual/source/topic/porting.rst b/mps/manual/source/topic/porting.rst
new file mode 100644
index 00000000000..b688876fd80
--- /dev/null
+++ b/mps/manual/source/topic/porting.rst
@@ -0,0 +1,10 @@
+.. _internals:
+
+Porting
+*******
+
+.. toctree::
+    :numbered:
+
+    plinth
+    platform