private classes and records aren’t visible outside of their assemblies anyway, so if they’re not extended inside the assemblies, they should be made explicitly non-extensible with the addition of the sealed keyword.

Noncompliant Code Example

private class MyClass  // Noncompliant
{
  // ...
}

private record MyRecord  // Noncompliant
{
  // ...
}

Compliant Solution

private sealed class MyClass
{
  // ...
}

private sealed record MyRecord
{
  // ...
}