LEGO patented the brick design with its modern tube-and-stud coupling system in 1958.
The 1958 design created the basic engineering principle behind modern LEGO bricks: studs on the top connect with tubes inside the brick below. This coupling gives models both clutch power and flexibility. Bricks can be separated, reused, and combined in countless arrangements while remaining stable enough for construction.
LEGO had already been making plastic bricks since 1949, but the earlier Automatic Binding Bricks did not use the same internal-tube design. The 1958 improvement solved a major weakness: models made from earlier bricks could be unstable and easy to knock apart. The new geometry made stronger structures possible and became the foundation of the modern LEGO system.
The patent date is important because LEGO’s basic brick design later became widely copied after patent protection expired. LEGO responded by emphasizing trademarks, minifigures, product design, quality control, and its distinctive brand identity. The compatibility of pieces from different decades is a direct consequence of the 1958 system.