The material is pine. 3/4" thick and comes in widths 3.5" or 5.5", generally. These boards can be found stapled together into long narrow boxes used for protecting products for transport. Things such as large industrial drill bits for instance. I found mine behind a manufacturing plant and they were paying me monthly to keep them hauled away. And after pleading with them to stop cutting them into short pieces, which they were doing to "help me" in hauling them, I ended up with rather long material in various lengths.
Then the prying began. The longest flat bar you can find is best for this. They're easy to find around a foot long but mine is 20". Next step is pulling the staples. All of this consumes time and is "my" least enjoyed activity in the project. Then all that's left till the finished product is the milling. The 3 steps remaining are to first, with a chop saw, cut off the the undesired portions and square the ends. I didn't cut to any certain lengths. Opting instead to get the maximum yield. I also skipped the 2nd step all together. But I recommend finding, in your new stacks of rough material, the boards with the least width and cutting them all to that demension. This 2nd step as well as the 3rd are done with a table saw.
The last step is a matter of creating an efficient repetition cause now every board must be rabitted on all four edges to facilitate the overlaps to shed the weather. After picking the nicest face of a board I cut each rabit in the same order. Two rabitted grooves showing on the face at the top and one end and the grooves on the back are cut into the bottom edge and on the opposite end as the face. I soon had stacks and stacks of this beautiful siding. And after covering my entire house with it I also have a beautiful house. The siding was a joy to install. The pieces slapped up quickly and nicely with ring shanked nails. It was so pretty that I couldn't bring myself to paint it. Just Thompson's water seal with UV block applied with a pump sprayer every other year has kept it in great condition these past six years of Houston, Texas weather.
This alternative did save me a small fortune in siding cost but the toil in time and effort to reclaim and repurpose the material was considerable. But the trade off of my time verses the money saved was very satisfactory to me. And I couldn't be happier with the end result. P.S. I'd have included pictures if I new how.