I have a short adapter like this for my dual boiler espresso machine. You can configure the machine to allow both boilers to come on simultaneously, which bring

I have a short adapter like this for my dual boiler espresso machine. You can configure the machine to allow both boilers to come on simultaneously, which brings the machine up to temperature faster, but requires a 20 amp circuit, or you can configure it to only allow one boiler to be on at a time (alternating between the two, when necessary), which takes longer to warm up initially, but allows you to use a 15 amp circuit. The machine has a 20 amp plug, because it's physically capable of drawing 20 amps. I have a 15 amp circuit, so I took extra care to enable the 15 amp mode and verify that it was working as intended. These cables can be okay to use if you understand what you're doing and are not violating the rules. They're obviously not supposed to be used to blindly ignore the wire or breaker ratings. It's like using `unsafe` in Rust. You're still absolutely not allowed to dereference null, even though you might be able to. You're telling the compiler, "I know you can't verify that what I'm doing is safe, but I promise that I've checked it, and it's fine." That's the same deal you're making when you use one of these cables.