David Hansen wrote:


Does the retaining strap, if it has not been stolen or broken,
prevent bikes hitting the carriage wall?

No. If there are two bikes on the hooks it just makes sure the metal
bits are in contact as they move around, ensuring the paint gets worn
off during the journey. That is also if the owner of the inner bike has
not undone them to get their bike out and not done them up again afterwards.

Tony