diff --git a/src/builder/code.rs b/src/builder/code.rs
index def72bb..a4d237a 100644
--- a/src/builder/code.rs
+++ b/src/builder/code.rs
@@ -103,21 +103,21 @@ impl<F> TypeRefBuilder<F> where F: Invoke<u32> {
     pub fn build(self) -> F::Result { self.callback.invoke(self.type_ref) }
 }
 
-pub struct FunctionsBuilder<F=Identity> {
+pub struct SignaturesBuilder<F=Identity> {
     callback: F,
     section: Vec<Signature>,
 }
 
-impl FunctionsBuilder {
+impl SignaturesBuilder {
     /// New empty functions section builder
     pub fn new() -> Self {
-        FunctionsBuilder::with_callback(Identity)
+        SignaturesBuilder::with_callback(Identity)
     }
 }
 
-impl<F> FunctionsBuilder<F> {
+impl<F> SignaturesBuilder<F> {
     pub fn with_callback(callback: F) -> Self {
-        FunctionsBuilder {
+        SignaturesBuilder {
             callback: callback,
             section: Vec::new(),
         }
@@ -133,13 +133,13 @@ impl<F> FunctionsBuilder<F> {
     }    
 }
 
-impl<F> FunctionsBuilder<F> where F: Invoke<SignatureBindings> {
+impl<F> SignaturesBuilder<F> where F: Invoke<SignatureBindings> {
     pub fn signature(self) -> SignatureBuilder<Self> {
         SignatureBuilder::with_callback(self)
     }
 }
 
-impl<F> Invoke<elements::FunctionType> for FunctionsBuilder<F> {
+impl<F> Invoke<elements::FunctionType> for SignaturesBuilder<F> {
 	type Result = Self;
 
 	fn invoke(self, signature: elements::FunctionType) -> Self {
@@ -147,7 +147,7 @@ impl<F> Invoke<elements::FunctionType> for FunctionsBuilder<F> {
     }    
 }
 
-impl<F> Invoke<u32> for FunctionsBuilder<F> {
+impl<F> Invoke<u32> for SignaturesBuilder<F> {
 	type Result = Self;
 
 	fn invoke(self, type_ref: u32) -> Self {
@@ -155,7 +155,7 @@ impl<F> Invoke<u32> for FunctionsBuilder<F> {
     }    
 }
 
-impl<F> FunctionsBuilder<F> where F: Invoke<elements::FunctionsSection> {
+impl<F> SignaturesBuilder<F> where F: Invoke<elements::FunctionsSection> {
     pub fn build(self) -> F::Result {
         let mut result = elements::FunctionsSection::new();
         for f in self.section.into_iter() {
@@ -171,31 +171,31 @@ impl<F> FunctionsBuilder<F> where F: Invoke<elements::FunctionsSection> {
 
 pub type SignatureBindings = Vec<Signature>;
 
-impl<F> FunctionsBuilder<F> where F: Invoke<SignatureBindings> {
+impl<F> SignaturesBuilder<F> where F: Invoke<SignatureBindings> {
     pub fn bind(self) -> F::Result {
         self.callback.invoke(self.section)
     }
 }
 
 /// New function builder.
-pub fn function() -> FunctionsBuilder {
-    FunctionsBuilder::new()
+pub fn signatures() -> SignaturesBuilder {
+    SignaturesBuilder::new()
 }
 
 #[cfg(test)]
 mod tests {
 
-    use super::function;
+    use super::signatures;
 
     #[test]
     fn example() {
-        let result = function()
+        let result = signatures()
             .type_ref().val(1).build()
             .build();
 
         assert_eq!(result.entries().len(), 1);
 
-        let result = function()
+        let result = signatures()
             .signature()
                 .param().i32()
                 .param().i32()
diff --git a/src/builder/import.rs b/src/builder/import.rs
new file mode 100644
index 0000000..1137aa5
--- /dev/null
+++ b/src/builder/import.rs
@@ -0,0 +1,39 @@
+use super::invoke::{Invoke, Identity};
+use elements;
+
+pub struct ImportBuilder<F: Identity> {
+    callback: F,
+    module: String,
+    field: String,
+    binding: ExternalBinding,
+}
+
+impl<F> ImportBuilder<F> {
+
+    pub fn with_callback(callback: F) -> Self {
+        ImportBuilder {
+            callback: callback,
+            module
+        }
+    }
+
+    pub fn external(self) -> ImportExternalBuilder<Self> {
+
+    }
+}
+
+pub struct ImportExternalBuilder<F=Identity> {
+    callback: F,
+    binding: ExternalBinding,
+}
+
+impl<F> ImportExternalBuilder<F> where F: Invoke<ExternalBinding> {
+    pub fn with_callback(callback: F) {
+        ImportExternalBuilder{
+            callback: callback,
+            binding: ExternalBinding::ExistingFunc(0),
+        }
+    }
+
+    pub fn 
+}
\ No newline at end of file
diff --git a/src/builder/misc.rs b/src/builder/misc.rs
index 9c6bc6e..6a18fd2 100644
--- a/src/builder/misc.rs
+++ b/src/builder/misc.rs
@@ -89,5 +89,4 @@ impl<F> ValueTypesBuilder<F> where F: Invoke<Vec<elements::ValueType>> {
     pub fn build(self) -> F::Result {
         self.callback.invoke(self.value_types)
     }
-}
-
+}
\ No newline at end of file
diff --git a/src/builder/mod.rs b/src/builder/mod.rs
index 599e40b..2972ffb 100644
--- a/src/builder/mod.rs
+++ b/src/builder/mod.rs
@@ -6,4 +6,4 @@ mod code;
 mod misc;
 
 pub use self::module::{module, ModuleBuilder};
-pub use self::code::function;
\ No newline at end of file
+pub use self::code::signatures;
\ No newline at end of file
diff --git a/src/builder/module.rs b/src/builder/module.rs
index 062fbca..dd272f5 100644
--- a/src/builder/module.rs
+++ b/src/builder/module.rs
@@ -1,5 +1,5 @@
 use super::invoke::{Invoke, Identity};
-use super::code::{self, FunctionsBuilder};
+use super::code::{self, SignaturesBuilder};
 use elements;
 
 /// Module builder
@@ -86,34 +86,39 @@ impl<F> ModuleBuilder<F> where F: Invoke<elements::Module> {
 
     /// Binds to the type section, creates additional types when required
     pub fn with_signatures(mut self, bindings: code::SignatureBindings) -> Self {
-        // todo bind to type section
-
-        {
-            let module = &mut self.module;
-
-            let raw_functions: Vec<u32> = bindings.into_iter().map(|binding|
-                match binding {
-                    code::Signature::Inline(func_type) => {
-                        module.types.types_mut().push(elements::Type::Function(func_type));
-                        module.types.types().len() as u32 - 1
-                    }
-                    code::Signature::TypeReference(type_ref) => {
-                        type_ref
-                    }
-                }
-            ).collect();
-
-            for function in raw_functions {
-                module.functions.entries_mut().push(elements::Func::new(function));
-            }
-        }
-
+        self.push_signatures(bindings);
         self
     }
 
+    /// Push signatures in the module, returning corresponding indices of pushed signatures
+    pub fn push_signatures(&mut self, signatures: code::SignatureBindings) -> Vec<u32> {
+        let module = &mut self.module;
+        let mut result = Vec::new();
+
+        // todo: maybe reuse existing types with the equal signatures
+        let raw_functions: Vec<u32> = signatures.into_iter().map(|binding|
+            match binding {
+                code::Signature::Inline(func_type) => {
+                    module.types.types_mut().push(elements::Type::Function(func_type));
+                    module.types.types().len() as u32 - 1
+                }
+                code::Signature::TypeReference(type_ref) => {
+                    type_ref
+                }
+            }
+        ).collect();
+
+        for function in raw_functions {
+            module.functions.entries_mut().push(elements::Func::new(function));
+            result.push(module.functions.entries_mut().len() as u32 - 1);
+        }
+
+        result
+    }
+
     /// Define functions section
-    pub fn functions(self) -> FunctionsBuilder<Self> {
-        FunctionsBuilder::with_callback(self)
+    pub fn functions(self) -> SignaturesBuilder<Self> {
+        SignaturesBuilder::with_callback(self)
     }
 
     /// Build module (final step)
diff --git a/src/elements/import_entry.rs b/src/elements/import_entry.rs
index 42bea48..fd08ae1 100644
--- a/src/elements/import_entry.rs
+++ b/src/elements/import_entry.rs
@@ -210,12 +210,36 @@ pub struct ImportEntry {
 }
 
 impl ImportEntry {
+    /// New import entry.
+    pub fn new(module_str: String, field_str: String, external: External) -> Self {
+        ImportEntry {
+            module_str: module_str,
+            field_str: field_str,
+            external: external,
+        }
+    }
+
     /// Module reference of the import entry.
     pub fn module(&self) -> &str { &self.module_str }
+
+    /// Module reference of the import entry (mutable).
+    pub fn module_mut(&mut self) -> &mut str {
+        &mut self.module_str
+    }
+
     /// Field reference of the import entry.
     pub fn field(&self) -> &str { &self.field_str }
+
+    /// Field reference of the import entry (mutable)
+    pub fn field_mut(&mut self) -> &mut str {
+        &mut self.field_str
+    }
+
     /// Local binidng of the import entry.
     pub fn external(&self) -> &External { &self.external }
+
+    /// Local binidng of the import entry (mutable)
+    pub fn external_mut(&mut self) -> &External { &mut self.external }    
 }
 
 impl Deserialize for ImportEntry {