You can draw inclined ceilings in CET. To do so, follow these steps:

1. Go to the Wall Drawing tab and pick either the Divided ceiling right or the Divided ceiling left tool:
   
   
   
   
2. Move the ceiling (which appears as a blue rectangle) into the drawing area. To place a ceiling that’s the same size as the room with existing walls, move the cursor to the point where your walls intersect and click to begin positioning.
   
   Snap to the outside edge of an intersection of the walls. This will automatically adjust the height of all walls fully covered by the ceiling once it is placed.
3. In the Quick Properties box that appears, enter the desired values for width & depth, or continue to snap to the ends of your walls. You can set the height and width for the position of the peak with mw (middle width), and Mid height. Confirm by pressing the Enter key or clicking. 
   
   

4. Before the third and last click, you will see this Quick Properties box:

    

   

    

   Depth: Length of the final line.
   mw: Distance from the first side placed to the highest point of the ceiling.
   Mid height: The height of the highest point of the ceiling.

Walls will automatically adjust heights/angles to fit the angle of the sloped portion of the ceiling as long as you snapped the ceiling to the outside of the walls.

Adjusting a divided ceiling after placement

Once a ceiling is placed, you can stretch it manually by clicking and dragging the three yellow snap points.

2D snap points:

1. Stretch the width of the divided ceiling.
2. Move the placement of the high point of the divided ceiling
3. Stretch the length of the divided ceiling.

3D snap points:

1. Stretch the width of the divided ceiling.
2. Move the placement of the high point of the divided ceiling
3. Stretch the length of the divided ceiling.
4. Stretch the height of the highest point of the ceiling.
   
   If the Locked property is disabled, this stretch point will instead adjust the inclination, instead of adjusting the whole flat surface's height.
   Enabling this property will revert the height into a flat side, and an inclined side.
5. Stretch the inclination of the inclined side.

The blue arrows found in a corner of a divided ceiling will rotate the direction of the divide.