Do I fix the sliding door to the wall or ceiling?

This depends on what type of sliding door you are looking for and the type of support structures on the wall or ceiling. If you want to install a traditional wall-sliding door, the sliding track can be installed on the wall on top of the doorway or the underside of the ceiling or embedded into the ceiling. Sliding pocket doors are typically installed by fixing them to the support structure inside the wall above the doorway. The sliding tracks of multiple sliding doors for storage rooms and industrial facilities are typically installed on the ceiling or, with regard to industrial buildings, for instance, the support beams. However, the most important thing is that the sliding track can be fixed to some type of support structure in multiple locations.