How K'Nex Works
Rods and connectors can join together in 3 ways – side on, end on, through the hole. To make a connection through the hole in the middle, simply put the rod through the hole. Note that a few special-purpose connectors don’t have a hole in the middle.
Blue and purple connectors have rectangular slots in them, which means you can connect two purple connectors to each other; two blue connectors to each other; or a blue connector to a purple connector. Put one slot inside the other slot, and push until you hear a click. Using blue and purple connectors together is very useful when making a 3-D model which needs corners. Connectors come in different shapes, with each correlating to an angle. White connectors are 360°, yellow 180°, red 90° and so on.
Don’t worry if you run out of rods. K’Nex rods can be joined together to form longer rods. Two white rods joined with a connector in a straight line is the same size as a yellow rod, for example.
Wheels come in different sizes and are composed of two separable parts: a grey wheel and a tyre. To allow the wheel to spin freely, put a rod through the hole in the wheel, and secure it with a connecter. The grey wheel can also be used alone for pulleys. In order to do this, you can insert the pin of a tan connector into the small hole of the grey wheel.
K’Nex pieces are fairly robust, so don’t be afraid to use a bit of force if pieces are not joining correctly. This is especially true of motors. These are the basic K’nex pieces, but there are lots more available, including motors. If you are having problems with your model, the chances are that it is because it is not symmetrical. Check to see if you have connector joined in a similar way at each side of the model, and that rod sizes are compatible. K’Nex is something that you need to experiment with for a while until you ‘get the hang of it’ and it does take a little time to get used to if you’ve not used it before.
Source: STEM North of Scotland