diff --git a/src/std/atomic.rs b/src/std/atomic.rs
index cc6354d..4beeb73 100644
--- a/src/std/atomic.rs
+++ b/src/std/atomic.rs
@@ -3,7 +3,7 @@
 
 pub mod plain;
 
-use std::{error::Error, marker::PhantomData, rc::Rc};
+use std::marker::PhantomData;
 
 use crate::core::*;
 use crate::std::*;
diff --git a/src/std/atomic/plain.rs b/src/std/atomic/plain.rs
index 0a1aea3..15169ef 100644
--- a/src/std/atomic/plain.rs
+++ b/src/std/atomic/plain.rs
@@ -1,7 +1,5 @@
 //! [`Plain`] type for storing raw byte sequnces.
 
-use std::fmt::Display;
-
 use crate::std::atomic::*;
 
 /// Raw bytes storage. Use [`Plain::raw`] to get the data.
diff --git a/src/std/collections.rs b/src/std/collections.rs
index c93897d..3061a44 100644
--- a/src/std/collections.rs
+++ b/src/std/collections.rs
@@ -1 +1,3 @@
+//! Standard generic collections.
+
 pub mod stack;
diff --git a/src/std/collections/stack.rs b/src/std/collections/stack.rs
index be3f01c..82bdd53 100644
--- a/src/std/collections/stack.rs
+++ b/src/std/collections/stack.rs
@@ -1,13 +1,20 @@
+//! Basic implementation of a stack/linked list.
+
 use crate::core::*;
+use crate::std::inlining::*;
 use crate::std::nullable::*;
 use crate::std::*;
 
+/// Node containing a (nullable) reference to the next node and an element.
 pub struct StackNode<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> {
+    /// Reference comes first due to being inlineable.
     pub rest: Stack<'a, Ctx, A>,
+    /// Unlike the original implementation in Python, doesn't default to using Point.
     pub element: Rc<A>,
 }
 
-type Stack<'a, Ctx, A> = Nullable<'a, Ctx, StackNode<'a, Ctx, A>>;
+/// Type representing a stack, an alias to a [Nullable] of a [StackNode].
+pub type Stack<'a, Ctx, A> = Nullable<'a, Ctx, StackNode<'a, Ctx, A>>;
 
 pub struct StackNodeFactory<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> {
     element_factory: A::Fctr,
@@ -106,16 +113,26 @@ impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> Factory<'a, Ctx>
     }
 }
 
+/// See [`StackVecResult`].
 pub type StackFaiure<'a, Ctx, A> = ResolutionFailure<'a, Ctx, StackNode<'a, Ctx, A>>;
 
+/// See [`StackVecWrapped`].
 pub type StackVecResult<'a, Ctx, A> = Result<Vec<Rc<A>>, StackFaiure<'a, Ctx, A>>;
 
+/// See [`ExtStack::vec`].
 pub type StackVecWrapped<'a, Ctx, A> = Wrapped<'a, Ctx, StackVecResult<'a, Ctx, A>>;
 
+/// Extention trait with helper methods for [Stack]s.
 pub trait ExtStack<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>>: Mentionable<'a, Ctx> {
+    /// Get an empty stack ([`Nullable::Null`]).
     fn empty(factory: A::Fctr) -> Self;
+    /// Get the corresponding factory.
     fn f(factory: A::Fctr) -> Self::Fctr;
+    /// Add one element.
+    ///
+    /// Note: consumes the stack. For non-consuming version do `.clone()` before adding.
     fn add(self, element: A) -> Self;
+    /// Collect all the elements into a [`Vec`].
     fn vec(self) -> StackVecWrapped<'a, Ctx, A>;
 }
 
@@ -204,3 +221,28 @@ mod tests {
         Ok(())
     }
 }
+
+impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> InlineableFactory
+    for StackNodeFactory<'a, Ctx, A>
+where
+    A::Fctr: InlineableFactory,
+{
+}
+
+impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> FixedSizeFactory
+    for StackNodeFactory<'a, Ctx, A>
+where
+    A::Fctr: FixedSizeFactory,
+{
+    fn size(&self) -> usize {
+        Stack::<'a, Ctx, A>::SIZE + self.element_factory.size()
+    }
+}
+
+impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> ConstSizeFactory
+    for StackNodeFactory<'a, Ctx, A>
+where
+    A::Fctr: ConstSizeFactory,
+{
+    const SIZE: usize = { Stack::<'a, Ctx, A>::SIZE + A::Fctr::SIZE };
+}
diff --git a/src/std/inlining.rs b/src/std/inlining.rs
index 8b13789..478d7b2 100644
--- a/src/std/inlining.rs
+++ b/src/std/inlining.rs
@@ -1 +1,191 @@
+pub mod staticpair;
 
+use super::atomic::*;
+use crate::core::*;
+use crate::std::*;
+
+pub trait InlineableFactory {}
+
+pub trait FixedSizeFactory: InlineableFactory {
+    fn size(&self) -> usize;
+}
+
+pub trait ConstSizeFactory: FixedSizeFactory {
+    const SIZE: usize;
+}
+
+pub trait InlineableObject<'a, Ctx: 'a + Context>: 'a {}
+
+pub trait FixedSizeObject<'a, Ctx: 'a + Context>: InlineableObject<'a, Ctx> {
+    fn size(&self) -> usize;
+}
+
+pub trait ConstSizeObject<'a, Ctx: 'a + Context>: FixedSizeObject<'a, Ctx> {
+    const SIZE: usize;
+}
+
+pub trait InlineableAtomic {}
+
+pub trait ConstSizeAtomic: InlineableAtomic {
+    const SIZE: usize;
+}
+
+impl<A: Atomic + InlineableAtomic> InlineableFactory for AtomicFactory<A> {}
+
+impl<A: Atomic + ConstSizeAtomic> FixedSizeFactory for AtomicFactory<A> {
+    fn size(&self) -> usize {
+        A::SIZE
+    }
+}
+
+impl<A: Atomic + ConstSizeAtomic> ConstSizeFactory for AtomicFactory<A> {
+    const SIZE: usize = A::SIZE;
+}
+
+impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> InlineableObject<'a, Ctx> for A where
+    A::Fctr: InlineableFactory
+{
+}
+
+impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> FixedSizeObject<'a, Ctx> for A
+where
+    A::Fctr: FixedSizeFactory,
+{
+    fn size(&self) -> usize {
+        self.factory().size()
+    }
+}
+
+impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> ConstSizeObject<'a, Ctx> for A
+where
+    A::Fctr: ConstSizeFactory,
+{
+    const SIZE: usize = A::Fctr::SIZE;
+}
+
+#[derive(Debug)]
+pub struct SizeError {
+    expected: usize,
+    received: usize,
+}
+
+impl Display for SizeError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_fmt(format_args!(
+            "expected {} bytes, read/wrote {} instead.",
+            self.expected, self.received
+        ))
+    }
+}
+
+impl Error for SizeError {}
+
+#[derive(Debug)]
+pub enum CheckedParseError<P: Error> {
+    Parse(P),
+    Size(SizeError),
+}
+
+impl<P: Error> Display for CheckedParseError<P> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            CheckedParseError::Parse(parse_error) => f.write_fmt(format_args!("{}", parse_error)),
+            CheckedParseError::Size(size_error) => {
+                f.write_fmt(format_args!("size check failed: {}", size_error))
+            }
+        }
+    }
+}
+
+impl<P: Error> From<P> for CheckedParseError<P> {
+    fn from(value: P) -> Self {
+        Self::Parse(value)
+    }
+}
+
+pub type CheckedParseResult<'a, Ctx, F> =
+    Result<<F as Factory<'a, Ctx>>::Mtbl, CheckedParseError<<F as Factory<'a, Ctx>>::ParseError>>;
+
+pub trait CheckedParse<'a, Ctx: 'a + Context>: FixedSizeFactory + Factory<'a, Ctx> {
+    fn deserialize_checked(
+        &self,
+        deserializer: &mut dyn Deserializer,
+        resolver: Rc<dyn Resolver<'a, Ctx>>,
+    ) -> CheckedParseResult<'a, Ctx, Self>;
+}
+
+pub trait CheckedSerialize<'a, Ctx: 'a + Context>: Serializable + FixedSizeObject<'a, Ctx> {
+    fn serialize_checked(&self, serializer: &mut dyn Serializer) -> Result<(), SizeError>;
+}
+
+impl<'a, Ctx: 'a + Context, F: FixedSizeFactory + Factory<'a, Ctx>> CheckedParse<'a, Ctx> for F {
+    fn deserialize_checked(
+        &self,
+        deserializer: &mut dyn Deserializer,
+        resolver: Rc<dyn Resolver<'a, Ctx>>,
+    ) -> CheckedParseResult<'a, Ctx, Self> {
+        let expected_size = self.size();
+        let start = deserializer.tell();
+        let result = self.deserialize(deserializer, resolver)?;
+        let end = deserializer.tell();
+        let received_size = end - start;
+        if received_size == expected_size {
+            Ok(result)
+        } else {
+            Err(CheckedParseError::Size(SizeError {
+                expected: expected_size,
+                received: received_size,
+            }))
+        }
+    }
+}
+
+impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx> + FixedSizeObject<'a, Ctx>>
+    CheckedSerialize<'a, Ctx> for A
+{
+    fn serialize_checked(&self, serializer: &mut dyn Serializer) -> Result<(), SizeError> {
+        let expected_size = self.size();
+        let start = serializer.tell();
+        self.serialize(serializer);
+        let end = serializer.tell();
+        let received_size = end - start;
+        if received_size == expected_size {
+            Ok(())
+        } else {
+            Err(SizeError {
+                expected: expected_size,
+                received: received_size,
+            })
+        }
+    }
+}
+
+pub trait AlwaysFixedSize {
+    fn _size(&self) -> usize;
+}
+
+impl<F: AlwaysFixedSize> InlineableFactory for F {}
+
+impl<F: AlwaysFixedSize> FixedSizeFactory for F {
+    fn size(&self) -> usize {
+        self._size()
+    }
+}
+
+pub trait AlwaysConstSize {
+    const _SIZE: usize;
+}
+
+impl<F: AlwaysConstSize> AlwaysFixedSize for F {
+    fn _size(&self) -> usize {
+        Self::_SIZE
+    }
+}
+
+impl<F: AlwaysConstSize> ConstSizeFactory for F {
+    const SIZE: usize = Self::_SIZE;
+}
+
+impl<F> AlwaysConstSize for PointFactory<F> {
+    const _SIZE: usize = HASH_SIZE;
+}
diff --git a/src/std/inlining/staticpair.rs b/src/std/inlining/staticpair.rs
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/src/std/inlining/staticpair.rs
@@ -0,0 +1 @@
+
diff --git a/src/std/nullable.rs b/src/std/nullable.rs
index 932d558..0f578f0 100644
--- a/src/std/nullable.rs
+++ b/src/std/nullable.rs
@@ -1,16 +1,19 @@
 //! This module introduces [`Option`]-like concepts into RADN typesystem using [`Nullable`].
 
+use super::inlining::*;
 use crate::core::*;
 use crate::std::*;
 
 /// Nullable reference type. Made for use as a linking element in data structures.
 pub enum Nullable<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> {
+    /// Unlike original Python implementation, stores the factory only in the null case.
     Null(A::Fctr),
     NotNull(Point<'a, Ctx, A>),
 }
 
 /// Nullable reference factory.
 pub struct NullableFactory<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> {
+    /// Factory of the referenced object.
     factory: A::Fctr,
 }
 
@@ -81,6 +84,7 @@ impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> Factory<'a, Ctx>
 }
 
 impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> Nullable<'a, Ctx, Nullable<'a, Ctx, A>> {
+    /// Reduce [Nullable] nesting.
     pub fn join(&self) -> Resolution<'a, Ctx, Nullable<'a, Ctx, A>> {
         match self {
             Nullable::Null(nullable_factory) => {
@@ -106,3 +110,9 @@ impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> Clone for Nullable<'a, Ctx,
         }
     }
 }
+
+impl<'a, Ctx: 'a + Context, A: Mentionable<'a, Ctx>> AlwaysConstSize
+    for NullableFactory<'a, Ctx, A>
+{
+    const _SIZE: usize = HASH_SIZE;
+}