Step 1- lay bottom towel rack and wall mount on its end as shown.
Step 2- insert bottom shelf onto nipples
Step 3- lock bottom shelf into place with couplings. - Hand tighten only needed.
Step 4- add 6" pipe plus coupling with nipple at end to both sides.
Step 5- place second shelf onto nipples and lock into place again with 2 couplings
Step 6- repeat step 5
And done !