LOC BLOCs was a plastic block construction toy set. Never reaching the popularity of Lego bricks, they did have a loyal following of fans. They were marketed in the 1970s and 1980s by Entex Industries, and manufactured in Japan as Dia Block by Kawada Co., which still produces sets to this day.
They were also sold by Sears, Roebuck and Co. under their house brand "Brix Blox." Today, similar blocks are still manufactured in Japan as Diabloks and sold in the U.S.A. under the name "Disney Build-It" blocks. The modern, Disney-branded blocks have also improved the incompatibility situation experienced by children owning this type of system.
The blocks were of a very similar grid pattern to the Lego system, but not quite. Rather than using a stud and tube system, Loc Blocs used a tall stud and short channels on the bottom of bricks. The tall studs were just tall enough to engage the channels. The knobs were too tall and spaced just a little bit off for fitting between Lego tubes. The result was that children who owned the much cheaper LOC BLOCs were often excluded from group play with other children who owned the more popular Lego bricks.