Hi Jurgen,

> Could you please explain more detailled how to select the inner piece?

Please check out these previous posts for some animations and additional descriptions:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1810.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=3324.4

But basically the 2 main things are that you'll want to do the window select starting on the left and dragging towards the right (the left-to-right direction will make a selection box that will only select things entirely inside the box), and normally to do a window select you need to do the initial mouse down in an empty area of the screen - if there is no empty area easily available then hold down both the shift + ctrl keys before clicking which will force a window selection and avoid doing an object drag which is what would normally happen when you click and drag the mouse on top of an object.

- Michael