diff --git a/src/dag/iter.rs b/src/dag/iter.rs
index 1d5a2f6..d0f7272 100644
--- a/src/dag/iter.rs
+++ b/src/dag/iter.rs
@@ -18,7 +18,8 @@ use crate::hash::HashWriter;
 use crate::node::Node;
 use crate::store::{Result, Store};
 
-pub struct Gap<'dag, S, HW>
+/// An iterator over the missing nodes in a DAG given a set of root nodes.
+pub struct Missing<'dag, S, HW>
 where
     S: Store<HW>,
     HW: HashWriter,
@@ -27,15 +28,17 @@ where
     search_nodes: BTreeSet<Vec<u8>>,
 }
 
-impl<'dag, S, HW> Gap<'dag, S, HW>
+impl<'dag, S, HW> Missing<'dag, S, HW>
 where
     S: Store<HW>,
     HW: HashWriter,
 {
+    /// Create an Iterator for the missing nodes given a set of root nodes.
     pub fn new(dag: &'dag Merkle<S, HW>, search_nodes: BTreeSet<Vec<u8>>) -> Self {
         Self { dag, search_nodes }
     }
 
+    /// Returns the next set of missing nodes in the iterator.
     pub fn next(&mut self) -> Result<Option<Vec<Node<HW>>>> {
         let nodes = self
             .dag
diff --git a/src/dag/mod.rs b/src/dag/mod.rs
index a5bcb26..286b365 100644
--- a/src/dag/mod.rs
+++ b/src/dag/mod.rs
@@ -158,11 +158,11 @@ where
     pub fn gap_fill_iter<'dag, 'iter>(
         &'dag self,
         search_nodes: BTreeSet<Vec<u8>>,
-    ) -> Gap<'iter, S, HW>
+    ) -> Missing<'iter, S, HW>
     where
         'dag: 'iter,
     {
-        Gap::new(self, search_nodes)
+        Missing::new(self, search_nodes)
     }
 
     /// Find the immediate next non descendant nodes in this graph for the given `search_nodes`.