I am curious how different people join bed rails to the footboard and headboard of an iron bed.

I'd bolt em. Depends alot on the design. I think you can buy steel units from Woodworker's Supply that could be made to work with metal.

Welcome aboard Dgause, glad to have you. If you'll put your general location in your header you may be pleasantly surprised to find out how many IFI folk live within visiting distance.

Bolts are good or mortice, tenon and wedges look nice and are solid joins that can easily be released if necessary.

Frosty The Lucky.

I took a very small piece of angle iron and welded it to the head and foot boards so the side rails rested on top of them. Then, I used threaded bolts to secure the side rails. You can have them go through the head and foot boards with the bolt heads showing. You can forge the bolt heads to provide more texture if needed. I tried to have the attaching mechanism not show. Good luck.

I have made 2 headboards, but my side verticals were made of square tube. I bolted the bed frame to it so it could be transported. One of them had a bed frame and I just made holes in the headboard to accommodate the frame, the other one I made my own bed frame.