When steel was the only material that frame builders used, there were many hand made custom bike frames, because there were many frame builders around, as steel was brazed together easily. There were many small manufacturers who build a few frames a year, but they were all unique and would be built to your specifications or whatever the builder wanted to sell you.
Now with everyone wanting alloy, carbon or titanium, most of these small steel frame builders have gone back to fixing water pipes, as some of them were only as good as plumbers. Most bicycle frames you buy now are “off the peg” and are mostly standard sizes, especially now with slopping frame geometries, small, medium and large, with some companies doing an extra small and extra large and also women’s geometry.
This is possible in alloy, steel and titanium as they are welded together, so a frame can be built to your specifications in these materials, but not in carbon fiber as the machines and moulds for each size cost a lot of money and cannot be set up for just one frame, unless you are a millionaire.
To have a frame made to fit you exactly, like a hand made suit, you have to be measured for it, this best done by the frame builder, but is usually done at your local bike shop. There are many systems for determining your frame specifications.
All your measurement will be taken, not just your leg length, your arm length, body, size of shoe, thigh length is very important, all will be put into a computer and the correct frame will be made for you, or it might turn out that a standard frame size will be just right any way.
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