Attempts to trademark the shapes of Kit Kats and London taxis have failed, opening the door for rivals to imitate them. So how come other products get to protect their distinctive shapes?
You know what a four-finger KitKat looks like. A quartet of slim wafer biscuits, linked together by their chocolate coating. Have a break, etc.
And even if you've never visited the city, it's likely you'll recognise the bulbous contours of a London black cab, which are every bit as much a symbol of the UK capital as Big Ben (although they do ply their trade in some other British cities).
But at the High Court this week, Mr Justice Arnold ruled that neither's shape is distinctive enough to trademark.
The London Taxi Company, manufacturer of the traditional hackney carriage, had taken action against the makers of the Metrocab, a new hybrid-powered taxi, saying its design had been "substantially copied" from its own.
But the judge dismissed the claim, opening the way for the Metrocab model to appear on London's streets over the next few years.
Likewise Nestle was denied the right to trademark its four-fingered KitKat in the UK when the court agreed with confectionery rivals Cadbury that its shape was not distinctive enough for consumers to identify all such bars as KitKats.
The existence of a similar bar produced in Norway since 1937 called Kvikk Lunsj (meaning "quick lunch"), which is available in some UK shops, did not help Nestle's case. The Swiss company says it will appeal.
It's rare for a three-dimensional object to be granted trademark status, but not unheard of. The shape of a four-finger KitKat may not be judged distinctive enough to qualify as a trademark, but those of Toblerone and Nestle's Walnut Whip are.
Coca-Cola first received the status for the contours of its bottle from the US Patent and Trademark Office as far back as 1960.
There can be huge benefits for firms that are granted trademark status. Unlike patents, which expire after 20 years, a trademark can potentially last forever - thus effectively conferring a long-term monopoly on a particular shape.
So how exactly do you go about getting one?
Firstly, the law requires that the shape is sufficiently distinctive, says Luke McDonagh, an expert in intellectual property law at City University London.
The point of this is to allow consumers to distinguish between different products - "the idea being that consumers would immediately recognise the shape itself and associate it with a particular brand, apart from any logos or brand name packaging".
The shape of toasters, for instance, has been judged "devoid of any distinctive character". A toaster is just a toaster. But a Toblerone is a Toblerone. It's not always an easy distinction to make, but "people know an elephant when they see one", says Iain Connor, partner in the intellectual property team at law firm Pinsent Masons.
In 2012 Lindt lost an attempt to trademark its chocolate bunnies because a European court ruled "the combination of the shape, the colours and the pleated ribbon with a small bell are not sufficiently different" from the wrapping of other chocolate rabbits.
In the KitKat case, Nestle cited a survey in which 90% of people shown a picture of the chocolate, without any names or symbols attached to it, mentioned KitKat. But Mr Justice Arnold ruled that the consumer relied "only on the word mark KitKat" and other branding to identify it - the chocolate being sold wrapped in packaging.
Likewise, in the black cab ruling, the same judge said the taxi was "merely a variation of the typical shape of a car" and "devoid of inherent distinctive character".
There's a second requirement. A trademark must not effectively give a technical monopoly to one company.
According to the Trade Marks Act 1994 - which implements the EU Trade Marks Directive - the shape must not be required to achieve a technical result, arise from the nature of the product itself, or give the product substantial value.
For instance, in a 2002 case, Philips tried to prevent Remington from marketing a three-headed shaver, which Philips said was its trademark. But the Court of Justice of the European Union (CJEU) ruled that the three-headed shaver was necessary to achieve a technical result, thus could not be protected - as a trademark would effectively give Philips the monopoly on producing that type of shaver.
A similar decision was made by the CJEU in 2010 in relation to the Lego bricks. The court ruled against them being protected, on the basis that this would prevent other companies from manufacturing a basic building toy.
However, in 2015 the court ruled that Lego people (known as mini-figures) were distinctive and their purpose was a human shape, not a technical function. In other words, they were more than just bricks, and thus should be protected.
Another recent case concerned Rubik's Cubes, which are registered as a trademark in the UK by a company called Seven Towns Limited (STL). A rival toy manufacturer argued trademarking the design gave STL a monopoly.
But the CJEU decided the cube's distinctive black separating lines were an aesthetic feature, not a technical one, as it would be possible to create a puzzle that did the same job without them.
Nonetheless, the bar for securing a trademark for a shape is "very high" because courts are wary of granting technical monopolies, says Connor.
"What the KitKat and black cab cases show is how difficult it is to gain protection for a three-dimensional shape," says McDonagh. While this can result in a challenge for designers, the purpose - in theory - is to protect consumers. Regardless of whether or not you can identify a popular chocolate-covered wafer snack at 100 paces.
More from the Magazine
Last year, manufacturer Nestle argued their four-fingered version of the chocolate-covered wafer snack should become a trademark in the UK, possibly preventing similar products being made. Justin Parkinson looked at the arguments for and against.
Subscribe to the BBC News Magazine's email newsletter to get articles sent to your inbox.