When it came to "universal" type assembly sets, I recall three distinct lines from my childhood. I'll start with the last my father purchased as it is one more people might know, Erector Set. https://en.wikipedia.org/wiki/Erector_Set The article provides the details, metal strips and plates perforated with holes through which one can insert screws fastened by nuts. The larger sets offered motors powered by electrical transformers one could plug into the wall socket. Elements like gears or pulleys could be attached to the motor's drive shaft to created actuated devices like cranes of even draw bridges. Funny, thinking about them now, I can "hear" the gentle "clanging" of the pieces, rather like flatware within a kitchen drawer. The next two are not as well known because they did not have the longevity of other building series like Lego. The closer parallel was called American Bricks. American Bricks Like Lego, the blocks had pins atop the block and an arrangement underneath that gripped the pins. But unlike Lego which came in a wide variety of colors and were for most part glass smooth, American Bricks were molded in just red and white. The red bricks had a texture along their perimeters that suggested, well, baked red clay bricks. The white pieces were meant to imply cinder clocks and concrete. As such, they were meant to depict "brick and mortar" structures like houses, shops and town halls. Oh, if one were inventive, one could build something that vaguely had the silhouette of a boat or a car, but admittedly Lego offered greater variation in its pieces to serve as a more "universal" construction set. On the other hand, American Bricks let someone build a structure that halfway resembled a conventional "middle American" brick home rather than a rainbow colored hideout for the Joker. The remaining set apparently aimed for the Lego audience but had its own particular design ethic, Tog'Ls (pronounced "toggles"). https://en.wikipedia.org/wiki/Tog'l Tog'Ls Whereas the "basic" Lego brick had 8 thick short pins atop a "brick with a 1 by 2 by 4 ratio (roughly), the basic Tog'L was a 1 by 1 by 1 cube with either a single pin upon one face 9or a second upon the face opposite and connection holes upon the remaining faces. One of these faces possessed a hinged 'lid" that could "toggle" open and closed. One could snap cubes together directly or alternate support pieces like white "girders" and green or orange tubes. the set allow contained blue "tacks" that could push into the hole punched faces or even protrude from them if one opened the little plastic "hatch" or "door". The primary color was a "road construction" yellow, with red being the next most common hue. Lego pieces were (and still are) cast in a very hard plastic, but I remember Tog'Ls feeling like an ever so slightly pliable poly-vinyl material. Oh, the edges were still quite well defined, but they didn't quite feel like glass shards when stepped upon them. Alas, they were sold for only two years before they ceased production in 1970. But i held onto the bulk of my collection until the latter 70s when my grandmother insisted we offer them in a yard sale. I bet we got less than two bucks for them. My American Bricks suffered the same fate.