I think just a clamp like a modern frame would. You can see one on these old frames too:
http://www.classiclightweights.co.uk/hybrid-lowry.html http://www.sterba-bike.cz/produkt/hobbs-of-barbican-semi-lightweight-c1950?lang=EN
I assume that's what you mean?
@jeff80 started
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I think just a clamp like a modern frame would. You can see one on these old frames too:
http://www.classiclightweights.co.uk/hybrid-lowry.html
http://www.sterba-bike.cz/produkt/hobbs-of-barbican-semi-lightweight-c1950?lang=EN
I assume that's what you mean?