A relatively common way of implementing a transfer or bypass/isolation function in North American electrical practice is to use mechanical means to interlock the handles of multiple circuit breakers or molded case switches so that they can't be both on at the same time. This can be done using a piece of metal retrofitted to a panelboard/loadcenter, or as part of a factory transfer switch assembly that uses circuit breakers or molded case switches as the electrical switching means.
However, the devices used to do this are designed around the North American busbar-mounted types of breakers. Breakers designed to the IEC standards typically mount to DIN rail instead, using a cable-in/cable-out construction, with a single row of breakers vs. the opposing-columns construction typical in North America. Is it possible to mechanically interlock this style of breaker (i.e. breaker A and breaker B cannot be on at the same time) without violating its approvals? If so, how is it done in practice?