Integrating a joint function in the cross-section is a design widely used in extrusion manufacture.
A movement of up to 180º can be achieved with only two extrusions. If a greater degree of movement is required, this can be achieved by introducing more parts.
The two joints shown above are very simple examples of this technique. The one on the right has a movement of approximately 40º. The one on the left has a movement of >90º and can be separated. Such a joint may be suitable for use with a movable cover.
This is a relatively common suggested design for interlocking joints between extrusions and has a very unwieldly shape, with a hinged column and a sliding hinged extrusion part inserted.
The heavy-duty design used to achieve the narrow column that the joint function is based on produces a tool that clearly has a propensity to damage. In addition, there is some doubt as to the integrity of the joint function as it is based on sliding surfaces and relatively close fit tolerances.