I need help with the interior trim. What is the trim around an interior door call? The trim around an interior door is called a casing. Casing can be made from a variety of materials, including wood, metal, or plastic. It is usually installed around the perimeter of an interior door to hide the gap between the door and the wall. Casing can also be used to add decorative detail to a door.

Most likely it's the door jamb. The jamb is the framing around a door or window. It's also where you would install a doorstop, which is a small piece of wood or metal that prevents the door from swinging open too far and hitting something else in the room.