@docmaggoo
I've looked at our and checked with dh.
We have load bars for the trailer, which allow us to use a roof rack bike rack on it.
Apparently you can get them for most trailers but they are specific to the trailer, check with your manufacturer what's appropriate.
Our trailer was 2nd hand and they came with it, otherwise I suspect dh would have just made some at work.
There are also some dedicated trailer bike racks available, but I think they are rarer.
For us, the advantage of buying a roof rack rack and using load bars on the trailer was that we can use it either way, with the car alone or with the trailer.
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