diff --git a/docs/assets/header.png b/docs/assets/header.png
index c92ef42a3..400903f7a 100644
Binary files a/docs/assets/header.png and b/docs/assets/header.png differ
diff --git a/docs/assets/header.svg b/docs/assets/header.svg
index 86b86408b..74e4457bc 100644
--- a/docs/assets/header.svg
+++ b/docs/assets/header.svg
@@ -29,16 +29,17 @@
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+ inkscape:cy="345.28144"
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inkscape:window-maximized="0"
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illustrations
+
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diff --git a/docs/rts/mm/cgc.md b/docs/rts/mm/cgc.md
new file mode 100644
index 000000000..1c92cd1a1
--- /dev/null
+++ b/docs/rts/mm/cgc.md
@@ -0,0 +1,9 @@
+---
+layout: page
+title: Concurrent Garbage Collection
+parent: Memory Management
+---
+
+# Concurrent Garbage Collection (CGC)
+
+TODO...
\ No newline at end of file
diff --git a/docs/rts/mm/header.md b/docs/rts/mm/header.md
index fb176ef0c..579b9dc12 100644
--- a/docs/rts/mm/header.md
+++ b/docs/rts/mm/header.md
@@ -22,7 +22,8 @@ to most-significant bit).
* Bits 28-29: the **pin type** of the object, used to distinguish between
pinned and unpinned objects.
* Bit 30: indicates whether or not the object is an **entanglement suspect**.
- * Bit 31: unused.
+ * Bit 31: the **mark bit**, used to mark live objects during
+ [Concurrent Garbage Collection](cgc.html).
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