Thanks for the anwsers and for the models you created. I think i should look at some tutorials, i still dont quite get it.

@rich o brien said:

I would move the barrels upwards to make the intersection between those and the frame more pronounced.

[attachment=2:otxhknck]<!-- ia2 -->solid.skp<!-- ia2 -->[/attachment:otxhknck]

The bottom part is now solid but some details are gone. To be exact the top baems of the frame were actually combined from one short (3 meters) and one long (6 meters) beam. Is it possible to have a solid where these two are still independent like the top and bottom beams of the frame?

@frederik said:

Here's a version of your model, where the parts are grouped and where possible, made into components...
Notice how small it is in size (byte-wise) compared to the original model...

Thank you too for the trouble.

But i cant still get the whole object into one solid. Am i missing something?

I see that the mistake I made was that if i wanted to add something i drew a rectangle on an existing object and then pulled it out. If i now try to do the same in an empty enviroment i see that it does not remain solid. I probably should have drawn every solid piece seperately and then use "outer shell" to combine them. But i feel like there should be a way to make a solid out if with the previously mentioned way.

For example if i draw a solid cube (attached image 1) and then draw a rectangle on it and pull it out (attached image 2) is it possible to make that into a solid? Or the only way to make it into a solid is to draw the second cube as a seperate solid and then merge them together?

Hello,

Im doing my first project in sketchup and thought i would try to 3d print it. I learned that for that i have to make it a solid component. When i tried it i got an error that some object are not solid. So i searched the net but couldnt find a solution because every problem i found was specific to that project. So i found a extension named "Solid inspector 2" and it found hundreds of errors in my project. Luckily it fixed them all and now says that there are no errors and everything should be shiny. Also after auto-fix some details turned gray instead of white they were before and some still remained white.
But when i try to make it a solid component i get the same error. At the moment i really dont have any ideas what could be wrong so i decided to ask for help.
I would be very thankful if anyone could find a time to look at my project and guide me in the right direction. I added the model to this topic.

solid.skp