How to judge the position of doors and windows on paper

The building profile is an orthographic drawing obtained by cutting the building with a vertical section according to the cutting position and projection direction indicated on the building plan. Drawings are viewed from the outside to the inside. When the river line of doors and windows is dotted, it proves that it is open inside, and when it is solid, it proves that it is open outside. The direction of the drawing is that the intersection of imaginary and solid lines is on the right, that is, open to the right, and the intersection is on the left, that is, open to the left.