Box kite
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A box kite is a classic high-performance kite. It was invented by Lawrence Hargrave in 1893.
The typical design has four parallel struts. The ends and box are made rigid with triangular arrangements of crossed struts. The ends are open. There are two sails, ribbons whose width is about 1/4 of the length of the box. The ribbons wrap around the ends of the box. In flight, one strut is the bottom, and the bridle is tied between the top and bottom of this strut. The dihedrals of the sails help stability.
Large box kites are constructed as cellular kites. Rather than one box, there are many, each with its own set of sails.
Most of the altitude records for kite flying are held by large box kites, with Dacron sails, flown with Spectra cable. Before Dacron, Spectra-cord and Kevlar were available, high performance box kites used oiled silk, linen or hemp sails, and were flown with steel cable. Silk, linen and hemp were used because they could be spun finer than cotton and stretched relatively little when wet. Steel had the highest available strength for its weight.
See also: kite flying