That old chestnut..

[Ricardoco]

I'm building a machine at the moment. I've gone for a mixture.

Where alu profile is handy I think, is being able to thread directly into the end of the profile (steel box section is hollow down the middle of course). So for example if you want to make an 'L' shape, you can bolt through the side of the steel section into the threaded end of the profile. Does that makes sense? That's my plan anyway.

makes sence to me, and I can see a pattern emerging here, lets run with it in the hope that other people chip in.

Draw here maybe