diff --git a/src/flat.rs b/src/flat.rs
index a8991206..6dfa0e4a 100644
--- a/src/flat.rs
+++ b/src/flat.rs
@@ -2,8 +2,43 @@ pub trait Encode {
     fn encode(&self, e: &mut Encoder) -> Result<(), String>;
 }
 
+impl Encode for bool {
+    fn encode(&self, e: &mut Encoder) -> Result<(), String> {
+        e.bool(*self);
+
+        Ok(())
+    }
+}
+
+struct Filler;
+
+impl Encode for Filler {
+    fn encode(&self, e: &mut Encoder) -> Result<(), String> {
+        e.zm_filler();
+
+        Ok(())
+    }
+}
+
+impl<T, K> Encode for (T, K)
+where
+    T: Encode,
+    K: Encode,
+{
+    fn encode(&self, e: &mut Encoder) -> Result<(), String> {
+        self.0.encode(e)?;
+        self.1.encode(e)?;
+
+        Ok(())
+    }
+}
+
 pub struct Encoder {
-    pub bytes: Vec<u8>,
+    pub buffer: Vec<u8>,
+    // Int
+    used_bits: usize,
+    // Int
+    current_byte: u8,
 }
 
 impl Default for Encoder {
@@ -14,7 +49,11 @@ impl Default for Encoder {
 
 impl Encoder {
     pub fn new() -> Encoder {
-        Encoder { bytes: Vec::new() }
+        Encoder {
+            buffer: Vec::new(),
+            used_bits: 0,
+            current_byte: 0,
+        }
     }
 
     /// Encode any type that implements [`Encode`].
@@ -26,4 +65,68 @@ impl Encoder {
     pub fn u8(&mut self, x: u8) -> Result<&mut Self, String> {
         todo!()
     }
+
+    /// Encode a `bool` value.
+    pub fn bool(&mut self, x: bool) -> &mut Self {
+        if x {
+            self.one()
+        } else {
+            self.zero()
+        }
+    }
+
+    fn zero(&mut self) -> &mut Self {
+        if self.used_bits == 7 {
+            self.next_word();
+        } else {
+            self.used_bits += 1;
+        }
+
+        self
+    }
+
+    fn one(&mut self) -> &mut Self {
+        if self.used_bits == 7 {
+            self.current_byte |= 1;
+            self.next_word();
+        } else {
+            self.current_byte |= 128 >> self.used_bits;
+            self.used_bits += 1;
+        }
+
+        self
+    }
+
+    fn next_word(&mut self) {
+        self.buffer.push(self.current_byte);
+
+        self.current_byte = 0;
+        self.used_bits = 0;
+    }
+
+    fn zm_filler(&mut self) {
+        self.current_byte |= 1;
+        self.next_word();
+    }
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn encode_true() {
+        let mut e = super::Encoder::new();
+
+        e.encode((true, super::Filler)).unwrap();
+
+        assert_eq!(e.buffer, vec![0b10000001]);
+    }
+
+    #[test]
+    fn encode_false() {
+        let mut e = super::Encoder::new();
+
+        e.encode((false, super::Filler)).unwrap();
+
+        assert_eq!(e.buffer, vec![0b00000001]);
+    }
 }