Looks great! What keeps the boxes of wire and vacuum from sliding out on a right turn?

let me know what it takes to attach to the ceiling. I  was trying to tap a self tapping metal screw into the roof for a tie down and using a 2-1/2" screw still couldn't get through to anything.  I've never tried to install much in cars or vans and didn't want to screw straight through the top!

I'm impressed and already planning out how to fit mine. Never fine any finish carpentry before, even as rough as this is.