Hi fraser,

> I managed to join all surfaces but can't get a solid out of them.

The attachment that I posted above had your object as a solid, here is a direct link to it:

http://moi3d.com/forum/get_attachment.php?webtag=MOI&hash=c925ce1225c8eb1ca889a9c83cb358d7&filename=mezzo_solid_3DM.zip

If you need to have a solid, will that version above work for you?

Like Burr mentions, the best way to see why your object is not a solid is to set up the "select naked edges" script on a shortcut key and use that.

Here is a direct link to that script:
http://kyticka.webzdarma.cz/3d/moi/#SelectNaked

To set it up, you go to Options > Shortcut keys, push "Add", then put in the key you want to trigger it on the left-hand column and paste in the script for the right-hand "Command" column. Then when you push that key all the unattached edges in your model will get selected so you can see where they are.

- Michael