Abstract: The modular rail assembly of the present invention includes at least one post, at least one rail, and at least one sleeve. The post is mounted to a surface and preferably extends upward. A sleeve is inserted into openings in the post. The openings are on opposite sides of the post. The sleeve preferably has a flange that contacts the post and prevents the sleeve from sliding completely thorough the openings. A rail is slid through the sleeve and preferably extends parallel to the surface. A single rail can extend through several posts. The sleeve acts as a buffer and protects the rail finish from being scratched or damaged by the post. Because of the sleeve, the modular rail assembly can be reassembled in any position without showing scratch marks or unpainted portions of the rail. In the preferred embodiment, a cap covers the top end of the post. There is also an opening in the cap into which a sleeve is inserted. A rail is slid through the sleeve and cap, similar to the rail and the post.