thanks for your help - here is what i got from it:
a) solid element operations tend to get messed up - especially when you already have a slanted wall and you want to make another slant within it
b) trim to roof works the best almost no errors
c) that slanted small wall method does work
![](/legacyfs/online/emojis/icon_smile.gif)
but only on straight walls (this is what i wanted) - doesn't work on already slanted ones
all in all trim to roof seem to be the best way to do it ... but this archicad has so much stuff to learn
![](/legacyfs/online/emojis/icon_smile.gif)
especially if you want to work with non-straight walls
thanks again will be back with more questions