The door seal is typically made from a temperature-resistant silicone, or rubber, with a hook located in each corner.
Note that there is also a visible join in the seal indicating where two sections have been joined together.
It is recommended that the join in the seal is placed at the bottom of the door. As heat rises, there is the possibility that the join could break. If this occurs whilst placed at the bottom then it will cause less of a problem than if it is at the top.