Detecting the problem is part of the solution. This has always been one of OTB's slogans in design work. One of his first pieces for B.D. was the Sardinel letter box (1973), which he designed jointly with Clotet. A problem had been detected: the ever-increasing volumes of correspondence and publicity had surpassed the capacity of the rather exiguous letter boxes in use at that time; and neither could the boxes accommodate the magazines and newspapers which were then beginning to be distributed via post.

    However, simply making the boxes bigger while maintaining the standard form would have meant taking up immense amounts of wall space; from this arose the idea of placing the letter boxes on edge, like bricks in rowlock formation - sardinel in Spanish. The letter boxes thus took on a tall, narrow and deep form, and could, like books on a shelf, be arranged into a compact block in the vestibule of a building.