diff --git a/util/src/trie/fatdb.rs b/util/src/trie/fatdb.rs
index 1b520d8ad..555e4644f 100644
--- a/util/src/trie/fatdb.rs
+++ b/util/src/trie/fatdb.rs
@@ -19,9 +19,10 @@ use sha3::Hashable;
 use hashdb::HashDB;
 use super::{TrieDB, Trie, TrieDBIterator, TrieError};
 
-/// A mutable `Trie` implementation which hashes keys and uses a generic `HashDB` backing database.
+/// A `Trie` implementation which hashes keys and uses a generic `HashDB` backing database.
+/// Additionaly it stores inserted hash-key mappings for later retrieval.
 ///
-/// Use it as a `Trie` or `TrieMut` trait object. You can use `raw()` to get the backing `TrieDB` object.
+/// Use it as a `Trie` or `TrieMut` trait object.
 pub struct FatDB<'db> {
 	raw: TrieDB<'db>,
 }
diff --git a/util/src/trie/fatdbmut.rs b/util/src/trie/fatdbmut.rs
index b699bf208..3e72c0653 100644
--- a/util/src/trie/fatdbmut.rs
+++ b/util/src/trie/fatdbmut.rs
@@ -20,8 +20,9 @@ use hashdb::HashDB;
 use super::{TrieDBMut, Trie, TrieMut, TrieError};
 
 /// A mutable `Trie` implementation which hashes keys and uses a generic `HashDB` backing database.
+/// Additionaly it stores inserted hash-key mappings for later retrieval.
 ///
-/// Use it as a `Trie` or `TrieMut` trait object. You can use `raw()` to get the backing `TrieDBMut` object.
+/// Use it as a `Trie` or `TrieMut` trait object.
 pub struct FatDBMut<'db> {
 	raw: TrieDBMut<'db>,
 }
diff --git a/util/src/trie/mod.rs b/util/src/trie/mod.rs
index 130406948..f6e731370 100644
--- a/util/src/trie/mod.rs
+++ b/util/src/trie/mod.rs
@@ -95,7 +95,7 @@ impl TrieFactory {
 	}
 
 	/// Create new immutable instance of Trie.
-	pub fn create<'db>(&self, db: &'db HashDB, root: &'db H256) -> Result<Box<Trie + 'db>, TrieError> {
+	pub fn readonly<'db>(&self, db: &'db HashDB, root: &'db H256) -> Result<Box<Trie + 'db>, TrieError> {
 		match self.spec {
 			TrieSpec::Generic => Ok(Box::new(try!(TrieDB::new(db, root)))),
 			TrieSpec::Secure => Ok(Box::new(try!(SecTrieDB::new(db, root)))),
@@ -104,7 +104,7 @@ impl TrieFactory {
 	}
 
 	/// Create new mutable instance of Trie.
-	pub fn create_mut<'db>(&self, db: &'db mut HashDB, root: &'db mut H256) -> Box<TrieMut + 'db> {
+	pub fn create<'db>(&self, db: &'db mut HashDB, root: &'db mut H256) -> Box<TrieMut + 'db> {
 		match self.spec {
 			TrieSpec::Generic => Box::new(TrieDBMut::new(db, root)),
 			TrieSpec::Secure => Box::new(SecTrieDBMut::new(db, root)),