@sirjohan said:

http://img855.imageshack.us/img855/1608/udm7.jpg
I have a problem eith my push/pull tool/knowledge. When i pull in this shape, the inside becomes empty. The floor in this case does not get solid. When i do it woth every other shape the "inside" of the shape is filled "solid" What do i do wrong?

This is because of the small sides.
Just press Ctrl when you push pull and you'll force the thickening mode.

Fredo