LEGO Brick

The 2x4 LEGO brick is eight studs on top and three hollow tubes underneath, and the tubes are the point. Pressed onto another brick, each stud is gripped between a tube and the walls: firm enough to build a tower, loose enough for a child to pull it apart. The company calls it clutch power, and because every brick it has made since 1958 is built to the same dimensions, every one fits every other.

LEGO's founder, Ole Kirk Christiansen, was a carpenter in Billund, in Jutland, and the company made wooden toys before it made plastic ones. From 1949 it sold Automatic Binding Bricks, based on a self-locking brick designed in England by Hilary Page for his firm Kiddicraft. They had studs on top and nothing beneath, and models built from them tended to come apart. In 1955 the founder's son, Godtfred Kirk Christiansen, turned the bricks into a System of Play, sets meant to be combined with one another, which made the grip problem urgent.

On 23 January 1958 Godtfred sat down with Axel Thomsen, who ran the German sales office, and sketched solutions on a sheet of paper. One of them was a row of tubes. Five days later, at 1:58 in the afternoon, the company filed its patent for 'a toy building element'. Six weeks after that Ole Kirk Christiansen died, and Godtfred took over a company whose future now rested on the brick.

The plastic changed in 1963, from cellulose acetate, which warps, to ABS, which does not, and colours, moulds and factories have changed many times. LEGO now makes some 36 billion elements a year in plants on three continents, to tolerances of a few thousandths of a millimetre. The brick has not changed. A 1958 brick that has not warped will press onto one bought today, which is as strict a reading of the sameness test as any object on this site can offer.