On the market:
1. Two ACBs one on top of the other, there are standard solid rod interlocking meninism by the OEM.
1.1 Two ACBs side by side or in different panels, there are standard flexible wire interlocking meninism by the OEM.
2. Two MCBs one on top of the other,???
2.1 Two MCBs side by side, there are standard interlocking meninism by the OEM.
3. Attention: Both breakers MUST also be electrically interlocked by (usually) under-voltage release NOT with shunt release!. This is to prevent inadvertent both breakers being closed at the same time.
Che Kuan Yau (Singapore)
PS: typo error "meninism" should be "mechanism"