The profiles are only attached at the corners. The corner castings have holes in them, and bolts go thru the holes from the inside, into square nuts in the back slot of the profiles. That's it. You can look up an exploded view in the "Spare Parts" page on Festool.com for a picture
The MDF top bolts down on top of the corner castings at each corner. It doesn't attach to the profiles at all.
