"bob" writes:

In hardware stores or warehouse the products are place in custome
shelf built with slotted angle posts.
Is there a light duty version for home use?

For example, I want a shelf that is 5 feet wide and 21 inches deep and
4 feet tall with a fix top, and two movable shelves inside. I looked
but found nothing close. Many shelves are 72 inches tall with a joint
in the middle of the posts. I want the posts to be 4 feet with no
joint.

Is there a system that has posts of various length, shelves of various
sizes that I can pick and combine?

Just asked a contractor I trust a similar question, but I was looking
for the highest quality stuff he's seen.

He sent me to Garage Tek.

It's not cheap, (I have a preliminary quote).
But it looks like you can get just about any arrangement you want.

--
Dan Espen