With some general-cargo ships of certain designs, additional special fittings might be required before a bulk grain cargo can be carried safely to protect against the cargo shifting dangerously when at sea. Most modern tweendeckers and multi-purpose vessels are designed to carry grain without special fittings, some being fitted with permanent ‘partial centre-line bulkheads‘, preventing the sideways shift of cargo. Older vessels engaging in this trade might require the construction of temporary wooden centre-line bulkheads before permission would be given to set out to sea. As we shall see later, true bulkcarriers are commonly fitted with ‘self-trimming‘ facilities for high stowing bulk cargoes such as grain. It is not usual for tweendeckers to have this facility although attention to this deficiency has been given by the designers of some modern multi-purpose vessels. The principle of hinged, hoistable tweendecks has also been utilised in modern multi-purpose vessels, such as the Freedom Mk II. With the revolution in cargo-handling, the design of general-cargo ships has had to adapt and conform to new methods. Consequently, the cargo spaces of modern multi-purpose vessels tend to be as square as is possible, so as to assist the stowage of containers and palletised-cargo, whilst on the weatherdecks, modern designs allow for storage of containers, often two or more tiers high, bearing in mind vessel stability, visibility from the bridge, and deck strengths. Older general-cargo vessels were designed to carry quantities of liquids – e.g. palm oil – and many had small ‘deep-tanks‘ fitted with heating coils for this purpose. Occasionally cargo holds, capable of being flooded to provide extra stability when the vessel is in ballast or partly-laden condition may be termed ‘deep-tanks’, although it is better to refer to them as ‘floodable-holds’ to distinguish their purpose. An example of a ‘floodable-hold’ in a general cargo vessel can be found by reference to cargo-hold No. 3 of the SD14. A very few modern multi-purpose types have been equipped with older-style deep-tanks, but generally this trade has been taken over almost totally by ‘parcel-tankers‘.