The recessed-key panel interlocking device is intended to provide a mechanical joint that can connect two panels using a single fastening key. Accordingly, the device connects two panels by interlocking uniform gaps and fingers that have been formed on the edges of each panel, by a small cylindrical key that holds them together. To accomplish this, a channel that can hold the key is formed along the edge region of both panels when the panels are oriented normally to one another. Further, when the panels are interlocked, the key is completely recessed within the panel material. Furthermore, while the panel edges that form the joint must be uniformly rectilinear and meet at right angles at the joint itself, beyond the joint they can assume any shape and bend to any angle, so that parts joined by the joint do not have to be panel-shaped or perpendicular to each other overall.