Usually it is resorted to only if the producer is compelled to attend to some other task, or lacks means for transporting the grain to the homestead. A platform consists essentially of a number of relatively straight poles laid horizontally on a series of upright posts. If the platform is constructed inside a building, it may be raised just 35-40 cm above ground level to facilitate cleaning and inspection. Platforms in the open may be raised at least 1 metre above ground level. They are usually rectangular in shape, but circular or polygonal platforms are common in some countries.
Grain is stored on platforms in heaps, in woven baskets or in bags.
In humid countries fires may be lit under elevated platforms, to dry the produce and deter insects or other pests. Instead of being horizontal and flat, the platform may be conical in shape, the point at the bottom. In southern Benin, Togo and Ghana, for example, maize cobs in their sheaths are laid in layers on circular platforms with their tips pointing inwards. The platforms are usually between 2 and 3 metres in diameter, but some may be more than 6 metres wide, with a maximum height of 2.5 metres at the centre and 1.5 metres at the periphery. Under prevailing climatic conditions most plant material rot fairly quickly, and most cribs have to be replaced every two or three years - although bamboo structures may last up to 15 years, with careful maintenance.