Abstract: A panelling assembly adapted to form a partition or wall by mere interlocking of the components and in particular by automatic locking of the panel by outward camming of associated parts upon mere resting of the panel in operative upright position. This panel assembly includes a baseboard, a panel having a groove in each of the two upright edges and bottom edge, a slat retractably held in each of the grooves of the upright edges, inclined slots and pins holding each slat in its groove and arranged to outwardly cam the slats whereby upon operative resting of the panel with engagement of the baseboard in the bottom groove thereof, the slats will be engaged by the baseboard and thus upwardly displaced and outwardly cammed into locking position. Upon mere lifting of the panel off the baseboard, the slats retract inwardly under gravity and the camming action produces retraction of the slats.