Hint W8 - Stub axles
Usually, K'NEX wheels slide right onto, or attach onto the end of, K'NEX rods.
The stub axle provides an alternative to this approach, for free-spinning wheels.
It can be attached onto the side of any classic K'NEX 5-way or 8-way connector, and incorporates a rod end onto which a classic K'NEX wheel can be fitted.
For instance, to support the front wheels of vehicles in which the rear wheels are driven by a motor.