Okay, you know the problem, storing raw metal stock, especially tubes and bars that are determined to roll off whatever surface you use for storage. Or maybe you've managed to contain them, but inevitably, the next piece you want to use is buried under all the rest.
Here's a suggestion for you to consider. It's worked well, for me.
In my case, the handiest place to store metal was under my “heavy bench”. If it was heavy before, it's really heavy, now.
These 2″-diameter PVC tubes are intended to be used for centralized vacuum cleaning systems. They're quite inexpensive and easy to find at local building centres.
Of course, they don't have to be placed under a workbench; that's just convenient in my case. For long stock, I have 1 m from one end of the bench legs to the other. For shorter lengths, I have 0.5 m from one side of the bench legs to the other. There's plenty of open space around this bench, permitting easy removal of even the longest pieces.
Underneath the lowest row, I provided a shelf made of 19 mm plywood. The vertical pieces at the each end fill in the space, so the tubes are held close together, and provide some support for the load, above. Because the PVC is so thin, it's important to keep them tight together, so the weight from above doesn't cause them to deform.
Seen from the side, there's a row of shorter tubes, with another shelf above them. This time, I used 19 mm particle board. (The simple truth is that I was using up scrap material and that's what was available at the time.) The vertical plywood spacers, as with the ones for the lower rows of tubes, fill in the spaces and help support the shelf, above. On top of all this, I have stock that isn't inclined to roll away.
If I need more storage, it will be a simple matter to cut some more tubes and add another row.
Although I mostly avoid really dusty things like woodworking, this bench is sometimes used for things that are pretty dirty, such as rusty metal that needs to be cleaned off. To help keep the metal stock more or less clean, I put some hooks under the bench top to hold curtains (also made of scrap material).
Pockets in the top and bottom of the curtains contain bar stock that supports them at the top and weights the bottom edges. Because I happened to have a fair supply of it, I use the pockets to store some 1/4″ brass brazing rod.
All closed up. This is the way the bench usually looks, but it's very easy to remove the curtains, when required.