There are a variety of intellectual property rights.
Registered and unregistered design right.
It’s unlikely that Patent applies here because there are no unique features.
They could have copyright in the shape and are registered or unregistered design right.
The test would be whether anyone looking at your sheet would look at it and think that it was a Bosch sheet.
The best situation here is to compare this to car spares. As soon as the car comes out, the pattern part manufacturers start making spares. Hence, if your car needs an exhaust, you would rarely buy a manufacturers part would buy a pattern part which is fit although maybe a slightly different design but is also much cheaper. I am not aware that any of these pattern part manufacturers have ever been taken to court provided of course they are not trying to pass the part off as original.
Similarly, you can buy jigsaw blades from a whole host of manufacturers which fit different jigsaws the fitting of which is unique to a particular manufacturer.
The difficulty of course is that if Bosch decided to bring an action against you for passing off and using exactly their shape, even though they may ultimately lose in court, (there is no guarantee they would lose, it is likely to be expensive and risky litigation.
Sometimes, there is no definitive answer to a question and all we can give you is an opinion of the likelihood of litigation.
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PS make sure that you are trading as a limited company and then, if they do start being difficult, and they take you to court, you can liquidate the company and their action will fall apart.