Finding the correct bolt size, thread pitch, material, and trusting that when I order grade 8 bolts, I’m actually getting grade 8 makes Amazon quite a pain in the ass.
If it’s something I don’t care too much about, yea Amazon is fine. But when I want to trust my life to it or it’s going to take some serious stress I’m going to want McMaster.
Besides all that manual labor requires math. A ton requires geometry.
You think plumbing, framing, electrical or any trade is done without measuring and quite complicated math?