A flatbed truck (or flatbed lorry in British English) is a type of truck the bodywork of which is just an entirely flat, level 'bed' with no sides or roof. This allows for quick and easy loading of goods, and consequently they are used to transport heavy loads that are not delicate or vulnerable to rain, and also for abnormal loads that require more space than is available on a closed body. Flatbed trucks can be either articulated or rigid. A flatbed has a solid bed, usually of wooden planks. There is no roof and no fixed sides. To retain the load there are often low sides which may be hinged down for loading, as a 'drop-side' truck. A 'stake truck' has no sides but has steel upright stanchions, which may be removable, again used to retain the load. Loads are retained by being manually tied down with ropes. The bed of a flatbed truck has tie-down hooks around its edge and techniques such as a trucker's hitch are used to tighten them. Weather protection is optionally provided by manually 'sheeting' the load with a tarpaulin, held down by ropes. These manual loading techniques are slow and require some care and skill. There is also the risk that an improperly secured load may be shed in transit, often leading to accidents or road blockages. There is also little theft protection for such a load. The slowness of loading loads like this led to the development of more efficient truck designs with enclosed bodies. Some improvement was made with the general replacement of ropes by flat webbing straps, tightened with a ratchet. These reduced the skill of 'roping up' and improved the control of tension, leading to fewer shed loads. Flatbeds became rare in the 1980s as the majority of road freight changed to either containers or pallet loads carried on larger and more efficient trucks, optimised for quicker loading by fork-lift trucks. Containers are carried on specialised semi-trailers with twistlocks in the corners to retain the container. Pallet loads are carried in either box bodies, loaded through rear doors, or curtain-sided bodies loaded through the sides.