Joining Roofs & effect of Rafter Cut

[Damo]

Here's a problem that been bugging me for a few days.

How come I can make the following roof, if the Rafter Cut property is 'Plumb Cut', but you get the error message "Can't make footprint roof" if you try and have the Rafter Cut property either 'Two-Cut - Plumb' or 'Two-Cut - Square'?

Also, taking the first condition (Plumb Cut, which is NOT what I want, but anyway.....) why can I 'Join Geometry' but not 'Join Roofs'

[beegee]

Sometimes, roofs - like the small hip at the front, won't behave when set to 2 cut type and sketched using " Pick Walls".

In these cases, I usually sketch by line, align to correct height and Join geometry.