When is a 'Clone' build amplifier a complete 'Knock off'?

It's interesting that identical clone products, copying the case work, design, electronics, badge and general look
are posted as clones for sale. When in fact they are cheaper Chinese made copies!

I had thought that a clone amp was something thats fundamentally a large nod to the electronic design but significantly changed
in it's appearance etc.

so the question is.... When is 'Clone' build amp a complete 'Knock off'