:)
A wire rack for mounting to the inner surface of a door of a cabinet so as to be able to open ... a generally trapezoidal device including in combination, ...
patents1.ic.gc.ca/claims?patent_number=1236069&language=EN - 11k -

It seems that the dispositivo trapézio was invented by a company called Hettich in 1955. First, here's what their Portuguese history page says:

"Em 1955 foi iniciado o fabrico de dispositivos de montagem, que em 1960 veio definir novos padrões construtivos com o surgimento do dispositivo de montagem Trapézio patenteado, com recobrimento visível. Este elemento não necessitava de buchas e tornou desnecessária qualquer furação de orifícios para buchas."

Now here's the corresponding English page:
"In 1955, connecting fittings were added to the product range, leading in 1960 to the patented, visible block connecting fitting that set new standards for furniture construction. This was a dowelless fitting, saving furniture manufacturers the effort of drilling dowel holes."

http://www.isaaclord.co.uk/products.aspx?subCat=19&parentCat...


http://www.doorhandlecompany.co.uk/scripts/doorfurniture.asp



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Note added at 1 day11 mins (2007-04-29 16:17:34 GMT)
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HERE YOU HAVE THE CONFIRMATION FOR SHELF STUD

http://www.hettich.com/hft/pro/media_hg/G08_90_95_en.pdf