It's a holiday weekend so I've had a little more time to get things done and also to create another post on the blog. Here is another method I have been using to attach buildings. Sometimes on a module, you need to hide things under a building. In this case I have mounted two Tortise switch motors inverted on top of the module.
I used scraps from the module construction to make posts that will reach the roofs in two places. Because the walls of a structure without a solid base tend to bow, I attach plastic angle to the module along where the inside of the wall will be to help maintain alignment.
Once everything seems to fit right, I drill a hole through the roofs and into the tops of the mounting posts.
A small wood or sheet metal screw is then used to secure the structure to the module. These can be easily hidden from view with rooftop details.
Here is this structure secured to the module but easily removal if access is ever needed to the electrical and mechanical components inside.