The K'NEX building system uses interlocking rods and connectors to make a huge number of different shapes, machines and vehicles. It's a simple system to use, with only a few rules and special connections to learn. You can, for example, put together a very simple and yet functional car out of K'NEX pieces in just a few minutes. It's a simple project that can quickly introduce someone to using the construction toy, as well as making a toy to play with.
Build the sides of your car. Clip two semicircular connectors to a yellow rod. Make a second unit. Connect the two in a rectangular shape using shorter, white rods. Make two of these units.
Make a box to form the body of the car. Push a navy blue rod into the connector, perpendicular to the body of the car. The rod will snap into place. This rod will become the first axle. Attach the other side to this rod, then attach a second axle to the back.
Slide the sides of the car inward enough to accommodate the wheels. On each rod, there's a solid piece at the end, with the ridged piece starting about 1/4-inch from the tip. If you're using a set of K'NEX wheels, the axle needs at least 3/4-inch. For a white, circular connector as a wheel, you only need about 1/2-inch.
Attach a wheel to the side of the vehicle on one of the axles. Clip it into place with a single-ended connector. Repeat with all four wheels. Plastic wheels with a rubber tread will have more traction and roll better, but you may not have a set of four on hand, so you can use white connector pieces.
Attach any finishing touches or accessories, such as a driver's seat or spoiler, to the car. When satisfied, test it by rolling it.