Abstract: A readily erectable and demountable lightweight sectional dock structure has cylindrical anchor posts arranged in a series of spaced pairs, stringers supporting deck plates, and cross braces. Clamp structures unite the stringers and cross braces independently to the posts and comprise a first U-shaped outer part with a semi-cylindrical post socket joined to leg portions having flat, interior, transversely extending, interlock surface portions removably joined to an inner clamp part with an opposing socket forming a merged continuation of the first part socket, the inner clamp part having longitudinally spaced, transversely extending socket legs with flat transversely extending exterior interlock surface portions abutting the interior surface portions on the outer clamp part, and transversely inwardly extending projections on the inner clamp parts receiving the cross braces telescopically.