You make dropouts! A delay from a supplier gave me just the push I needed to make some custom dropouts for the Griego cross bike. Made out of .19" 4130 plate, drops like these are much stronger than the average mild steel most manufacturers use. The mild steel is usually strong enough, but if you're making your own, why use the cheap/weak stuff?
Here's the right drop about 70% done. It will get further shaping, a rack mount, the hanger drilled/tapped. possibly a window, and stainless faces.......whew, maybe it's more like 50% done!