1)Start at the top left corner of the white outlines the door provides
2)Draw the line over 2 the top right corner of the white outlines
3)Draw the line 2 the bottom left corner of the white outlines
4)Draw the line over 2 the bottom right corner of the white outlines
5)Finish off the crest by drawing ur line 2 the top left corner

Hope this helps!:)