diff --git a/apps/math_toolbox.cpp b/apps/math_toolbox.cpp
index 00a32610a..f5dd35a86 100644
--- a/apps/math_toolbox.cpp
+++ b/apps/math_toolbox.cpp
@@ -1,4 +1,5 @@
 #include "math_toolbox.h"
+#include "global_preferences.h"
 #include "./shared/toolbox_helpers.h"
 #include <assert.h>
 #include <string.h>
@@ -384,3 +385,13 @@ MessageTableCellWithChevron* MathToolbox::nodeCellAtIndex(int index) {
 int MathToolbox::maxNumberOfDisplayedRows() {
  return k_maxNumberOfDisplayedRows;
 }
+
+int MathToolbox::indexAfterFork() const {
+    Preferences::UnitFormat unitFormat = GlobalPreferences::sharedGlobalPreferences()->unitFormat();
+    if (unitFormat == Preferences::UnitFormat::Metric) {
+      return 0;
+    }
+    assert(unitFormat == Preferences::UnitFormat::Imperial);
+    return 1;
+}
+
diff --git a/apps/math_toolbox.h b/apps/math_toolbox.h
index 77bc6bd56..41eb996fa 100644
--- a/apps/math_toolbox.h
+++ b/apps/math_toolbox.h
@@ -15,6 +15,8 @@ protected:
   int maxNumberOfDisplayedRows() override;
   constexpr static int k_maxNumberOfDisplayedRows = 6; // = 240/40
 private:
+  int indexAfterFork() const override;
+
   MessageTableCellWithMessage m_leafCells[k_maxNumberOfDisplayedRows];
   MessageTableCellWithChevron m_nodeCells[k_maxNumberOfDisplayedRows];
 };
diff --git a/escher/include/escher/toolbox.h b/escher/include/escher/toolbox.h
index e38df51ed..f128f54eb 100644
--- a/escher/include/escher/toolbox.h
+++ b/escher/include/escher/toolbox.h
@@ -25,9 +25,12 @@ protected:
   bool returnToPreviousMenu() override;
   virtual int maxNumberOfDisplayedRows() = 0;
   virtual const ToolboxMessageTree * rootModel() const = 0;
+  /* indexAfterFork is called when a fork-node is encountered to choose which
+   * of its children should be selected, based on external context. */
+  virtual int indexAfterFork() const { assert(false); return 0; };
   MessageTableCellWithMessage * leafCellAtIndex(int index) override = 0;
   MessageTableCellWithChevron * nodeCellAtIndex(int index) override = 0;
-  mutable ToolboxMessageTree * m_messageTreeModel;
+  mutable const ToolboxMessageTree * m_messageTreeModel;
   /* m_messageTreeModel points at the messageTree of the tree (describing the
    * whole model) where we are located. It enables to know which rows are leaves
    * and which are subtrees. */
diff --git a/escher/include/escher/toolbox_message_tree.h b/escher/include/escher/toolbox_message_tree.h
index 1e17b83b0..ba8ac5005 100644
--- a/escher/include/escher/toolbox_message_tree.h
+++ b/escher/include/escher/toolbox_message_tree.h
@@ -15,23 +15,23 @@ public:
         stripInsertedText);
   };
   template <int N>
-  constexpr static ToolboxMessageTree Node(I18n::Message label, const ToolboxMessageTree (&children)[N]) {
+  constexpr static ToolboxMessageTree Node(I18n::Message label, const ToolboxMessageTree (&children)[N], bool fork = false) {
     return ToolboxMessageTree(
         label,
         (I18n::Message)0,
         (I18n::Message)0,
         children,
-        N,
+        fork ? -N : N,
         true);
   }
   template <int N>
-  constexpr static ToolboxMessageTree Node(I18n::Message label, const ToolboxMessageTree * (&children)[N]) {
+  constexpr static ToolboxMessageTree Node(I18n::Message label, const ToolboxMessageTree * (&children)[N], bool fork = false) {
     return ToolboxMessageTree(
         label,
         (I18n::Message)0,
         (I18n::Message)0,
         children,
-        N,
+        fork ? -N : N,
         true);
   }
   const MessageTree * childAtIndex(int index) const override {
@@ -40,6 +40,7 @@ public:
   I18n::Message text() const { return m_text; }
   I18n::Message insertedText() const { return m_insertedText; }
   bool stripInsertedText() const { return m_stripInsertedText; }
+  bool isFork() const { return numberOfChildren() < 0; }
 private:
   constexpr ToolboxMessageTree(I18n::Message label, I18n::Message text, I18n::Message insertedText, const ToolboxMessageTree * children, int numberOfChildren, bool stripInsertedText) :
     MessageTree(label, numberOfChildren),
diff --git a/escher/src/toolbox.cpp b/escher/src/toolbox.cpp
index e4848e8bd..9fe23d8b5 100644
--- a/escher/src/toolbox.cpp
+++ b/escher/src/toolbox.cpp
@@ -39,7 +39,7 @@ void Toolbox::willDisplayCellForIndex(HighlightCell * cell, int index) {
 }
 
 int Toolbox::typeAtLocation(int i, int j) {
-  MessageTree * messageTree = (MessageTree *)m_messageTreeModel->childAtIndex(j);
+  const MessageTree * messageTree = m_messageTreeModel->childAtIndex(j);
   if (messageTree->numberOfChildren() == 0) {
     return LeafCellType;
   }
@@ -48,7 +48,11 @@ int Toolbox::typeAtLocation(int i, int j) {
 
 bool Toolbox::selectSubMenu(int selectedRow) {
   m_selectableTableView.deselectTable();
-  m_messageTreeModel = (ToolboxMessageTree *)m_messageTreeModel->childAtIndex(selectedRow);
+  m_messageTreeModel = static_cast<const ToolboxMessageTree *>(m_messageTreeModel->childAtIndex(selectedRow));
+  if (m_messageTreeModel->isFork()) {
+    assert(m_messageTreeModel->numberOfChildren() < 0);
+    m_messageTreeModel = static_cast<const ToolboxMessageTree *>(m_messageTreeModel->childAtIndex(indexAfterFork()));
+  }
   return NestedMenuController::selectSubMenu(selectedRow);
 }
 
@@ -56,15 +60,14 @@ bool Toolbox::returnToPreviousMenu() {
   m_selectableTableView.deselectTable();
   int currentDepth = m_stack.depth();
   int index = 0;
-  // We want to get the current ToolboxMessageTree's parent ToolboxMessageTree,
-  // but there is no ToolboxMessageTree::getParent() method. We thus have to
-  // start from the root ToolboxMessageTree and sequentially get the selected
-  // child until it has the wanted depth.
   ToolboxMessageTree * parentMessageTree = (ToolboxMessageTree *)rootModel();
   Stack::State * previousState = m_stack.stateAtIndex(index++);
   while (currentDepth-- > 1) {
     parentMessageTree = (ToolboxMessageTree *)parentMessageTree->childAtIndex(previousState->selectedRow());
     previousState = m_stack.stateAtIndex(index++);
+    if (parentMessageTree->isFork()) {
+      parentMessageTree = (ToolboxMessageTree *)parentMessageTree->childAtIndex(indexAfterFork());
+    }
   }
   m_messageTreeModel = parentMessageTree;
   return NestedMenuController::returnToPreviousMenu();