On the base of the frame with rivets fixed supporting parts
To the middle part of the frame I fixed the holders. Also with the help of rivets, which then flattened and scraped.
Also in the middle part, I drilled a lot of holes for fixing the motherboard, video card, drive, and cut the threads into them. A large hole in the center is for PCI-Express riser.
Then I installed the middle part of the frame on the base, fastened it with rivets, and cut off and cleaned the holders.