A normal roof means that your car has no special fastening systems. On a normal roof, the roof racks are attached to the door frames with a clamping system. Here it is of course useful if your car is equipped with 4 doors. On many cars with this system you can often find holes in the upper door frame. This is where the individual clamps are connected to the frame. However, this is not always the case or a prerequisite.
The open railing is the classic railing. It is mounted on the roof so that there is still a little space between the railing and the car roof. This type of railing is generally great for a roof rack and roof tent. However, you should make sure that the railing is stable enough. With a long car roof, it is useful if a profile is attached centrally by the manufacturer to provide additional support for the railing.
The system is similar to the open railing. The difference here is that the rail has no space between the rail and the car roof. This means that the rail lies directly on the car roof and is super stable.
A rain gutter as a roof rack system is often found on older cars these days. With this system, you have a gutter either above the window frame or at the edge of the car roof, where you can clamp and screw the roof racks.
The roof rack system with fixed points is often found on multivans or buses. But this system can also be found on smaller cars. The fixed points are a stable and simple system. Here, the roof rack is connected directly to the car roof with screws. Often there are plastic covers on the roof. These cover the thread where the roof rack foot is screwed on.
T-slot profiles and rail kits
As the name suggests, this roof rack system has rails in the roof of the vehicle. Screws are inserted into this system, onto which the roof rack base is then attached.