diff --git a/book/art/forks-pruned2.bob b/book/art/forks-pruned2.bob
new file mode 100644
index 0000000000..64e3d4cb1f
--- /dev/null
+++ b/book/art/forks-pruned2.bob
@@ -0,0 +1,11 @@
+ 1
+ |
+ 3
+ |\
+ | \
+ |  |
+ |  |
+ |  |
+ 6  |
+    |
+    7
diff --git a/book/src/bank-forks.md b/book/src/bank-forks.md
index 5bed9fd2a9..771e04c7aa 100644
--- a/book/src/bank-forks.md
+++ b/book/src/bank-forks.md
@@ -1,4 +1,4 @@
-# Bank Fork
+# Bank Forks
 
 This design describes a way to checkpoint the bank state such that it can track
 multiple forks without duplicating data.  It addresses the following
@@ -11,8 +11,9 @@ challenges:
 
 ## Architecture
 
-The basic design idea is to maintain a DAG of forks. The DAG is initialized with
-a *root*.  Each subsequent fork must descend from the root.
+The basic design idea is to maintain a DAG of Banks checkpointed at different
+slot heights. The DAG is initialized with a *root* slot height.  Each
+subsequent fork must descend from the root.
 
 ## Active Forks
 
@@ -25,35 +26,35 @@ For example:
 
 The following *active forks* are in the forks DAG
 
-* 4,2,1
-* 5,2,1
-* 6,1
-* 7,1
+* {4, 2, 1}
+* {5, 2, 1}
+* {6, 3, 1}
+* {7, 3, 1}
 
-## Merging into root
+## Squashing
 
-A validator votes for a frozen fork.  The *active fork* connecting the fork
-to the root is merged.  If the *active fork* is longer than
-`Forks::ROLLBACK_DEPTH` the oldest two forks are merged.  The oldest fork in
-the *active fork* is the current root, so the second oldest is a direct
-descendant of the root fork.  Once merged, the current root is updated to the
+A validator votes for a frozen fork.  The active fork connecting the fork to
+the root is *squashed*.  If the active fork is longer than
+`Forks::ROLLBACK_DEPTH` the oldest two forks are squashed.  The oldest fork in
+the active fork is the current root, so the second oldest is a direct
+descendant of the root fork.  Once squashed, the current root is updated to the
 root descendant. Any forks that are not descendants from the new root are
 pruned since they are no longer reachable.
 
-For example:
+Starting from the example above, consider a vote on 5 versus a vote on 6:
 
 <img alt="Forks" src="img/forks.svg" class="center"/>
 
-* ROLLBACK\_DEPTH=2, vote=5, *active fork*={5,2,1}
+* ROLLBACK\_DEPTH=2, vote=5, *active fork*={5, 2, 1}
 
 <img alt="Forks after pruning" src="img/forks-pruned.svg" class="center"/>
 
 The new root is 2, and any active forks that are not descendants from 2 are
 pruned.
 
-* ROLLBACK\_DEPTH=2, vote=6, *active fork*={6,1}
+* ROLLBACK\_DEPTH=2, vote=6, *active fork*={6, 3, 1}
 
-<img alt="Forks" src="img/forks.svg" class="center"/>
+<img alt="Forks" src="img/forks-pruned2.svg" class="center"/>
 
-The tree remains with `root=1`, since the *active fork* starting at 6 is only 2
+The tree remains with `root=1`, since the active fork starting at 6 is only 2
 forks long.