Abstract: The invention relates to an assembly device for elements of the type comprising a framework and at least one spacer or panel extending transversely to said framework. In accordance with the invention, the device comprises two assembly bodies (100, 200) insertable in respective hollow bars constituting a portion of the framework, each assembly body having a central locking portion (101, 201) capable of penetrating into a hole in a panel to be supported, together with a peripheral portion (102, 202) capable of bearing against one of the faces of said panel; the central locking portions (101, 201) constitute a sloping ramp bayonet coupling, thereby enabling said bodies to be deformed radially outwards by relative rotation between the two assembly bodies, thus locking them automatically in the associated hollow bars. The invention is applicable, in particular, to pieces of furniture for provision in kit form, and for various types of element and/or hollow bar.