hi rose u need to make the windows negative under theire atributes settings click the litle a and the wall positive then group all windows and the wall. hope this helps start with a square window and a wall to get the principle. then make a boolean group for the window u want a tube ontop of an elongated cube group them and make this group negative then duplicate this group and add a wall and group again. hope this clarifies things for you. bye bye

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