Each wheel well has a traction spring which pushes down on a finger in the housing, keeping the wheels firmly on the ground.

The finger rides along a bushing on the side of the wheel.

The spring-loaded fingers must be pushed up into the housing all the way, and then the wheels inserted underneath them so that the spring rests on the bushing.

The leeway for keeping the wheel in the appropriate location while all of the screws are removed from the wheel well is very small, so compression must be applied constantly between the wheel and wheel well to prevent the spring from dislodging.

The wheel should be fighting you constantly. If it is not, restart by setting the spring back onto the bushing.