I wanted a corner shelf unit for my living room and HEJNE storage racks seems to be a good choice for it. But I did not want to just place 2 HEJNE racks at an angle to each other and call it a day, so I figured out how to turn two HEJNE storage racks into a corner shelf unit.
Get two of the HEJNE shelves and place them at 90 degrees, the short side of one shelf butting the long side of the other shelf. Mark where the pieces should join.
Then connect the two HEJNE shelves with plastic angle connectors. Drill pilot holes for the screws before screwing in the plastic connectors. It is also a good idea to reinforce the connection with a dab of wood glue before screwing them on.
Then simply assemble the HEJNE shelves to the posts as per IKEA instructions to turn it into a corner shelf unit.
Note: Obviously, without the two HEJNE posts in the middle, the HEJNE corner shelf unit will not be as strong and sturdy as the original HEJNE construction. I would not place my family heirloom in the middle unsupported section. Hack but use your judgement too.