The plastic tubes that are between each shelving unit are supposed to screw into the one above it.  12 tubes - and I could only get 2 on the second shelf screwed in.  Terrible plastic extrusion made it impossible to get the shelves in place and I did not want to use a wrench and tear up the plastic tube.  Fortunately, they included the phone number and I called them and they are sending me new tubes.  I instructed them to ensure that they could correctly screw them together before sending them out to me.  Minimum 10 days before I receive them.