Standard shipping containers have fixed internal dimensions, and plenty of legitimate cargo simply does not fit inside them — industrial machinery, structural steel, large vehicles, and similar equipment. Out-of-Gauge (OOG) shipping and flat-rack or open-top containers exist specifically for this category of cargo.
Open-top containers remove the standard roof, allowing cargo to be loaded from above or cargo that exceeds standard height to protrude slightly (within carrier-approved limits) with a tarpaulin cover. Flat-rack containers remove the sides entirely, leaving just a base and end walls — suited to oversized, irregular, or heavy machinery that needs to be loaded from the side or top by crane.
True Out-of-Gauge cargo, exceeding even flat-rack dimensions, is typically shipped as break-bulk — loaded and secured individually rather than inside any container at all. This is the most specialized end of ocean freight, and pricing reflects the additional handling, securing, and often escort requirements involved.
Early planning matters more here than almost anywhere else in shipping — the equipment has to be booked in advance, and documentation requirements are more involved than standard cargo. Transeasy's project portfolio includes exactly this kind of work, including over ten specialized containers moved to Mexico and a 30-tonne overweight delivery to India. If your cargo does not fit a standard container, that is the first thing to flag, before anything else gets planned around it.