Educational toy made in plastic versions. In the mid-1950s, more explicitly engineering-themed construction toys appeared, including plastic girders, columns, and panels that could be assembled into a model curtain wall skyscraper. Later, this Girder and Panel structural system was extended to a Hydro-Dynamic setup by adding pipes, valves, tanks, nozzles, and pumps to allow construction of model plumbing, HVAC, and chemical engineering systems like a simulated distillation column. Other extensions of the system supported suburban-style housing developments (Build-A-Home), or monorail transportation systems (Skyrail). The building toy Lego was originally developed by Ole Kirk Christiansen in Billund, Denmark, in the 1930s. The name
EXÍN Castles yet still interoperable with generic Lego, gave increased competition to EXIN. EXÍN Castles EXÍN Castillos (or EXIN Castles) is a construction toy. First introduced by the Exin Lines Brothers in 1968 in Barcelona, Spain, this plastic block toy was designed for the construction of castle-like-buildings. The company has most recently produced Castle lines toys for the Shrek movie franchise and others. The EXIN Castillos blocks are of a peg-and-socket design similar to Lego, though with larger pegs, and the most common size being a 1x2 design (whereas 2x4 is the most common Lego size). The blocks are usually a mottled