diff --git a/cb/cb.factor b/cb/cb.factor
index 3ad0957..0bc0833 100644
--- a/cb/cb.factor
+++ b/cb/cb.factor
@@ -44,8 +44,16 @@ TUPLE: cb-node < node byte# bits ;
 ! ** Insertion
 ! Explain...
 
+! Keep the byte sequence of the current key in =key-bytes= and provide a working
+! environment for it with =with-key=.
+SYMBOL: key-bytes
+
+: with-key ( key quot -- )
+    [ key-bytes ] dip with-variable ; inline
+
 DEFER: cb-set
 
+! TODO Rewrite with =with-key=.
 : cb-insert ( value key node -- node taller? created? )
     2dup [ byte#>> ] [ bits>> ] bi
     [ swap get-byte-at ] dip key-side [