Architraves - Timber moulding fitted to the surrounds of internal doors.
They are designed to hide the untidy area where the walls meet the door frame. There are many styles of architrave from a simple bullnose to deep moulded architraves.
Architraves are fitted by cutting a 45 degree angle at the tops so the pieces butt up against each other (mitre joint), they are then fitted to the door frame using 30mm pins. Use a nail punch to sink the heads of the pins.
Below is a 3D image that shows Architraves. You can move the 3D object around with your mouse.