A mounting mechanism for connecting a tractor unit to a guide track, the mounting mechanism includes a fixed block having a first set of rolling devices and a movable plate having a second set of rolling devices. The distance between the first and second sets of rolling devices is adjustable by moving the movable plate to engage or disengage the tractor unit to the guide track. A clamping assembly is provided with a shaft, cam spring, and cam handle for adjusting the distance between the first and second rolling devices. When the cam handle is in an open position, the distance between the rolling devices is greater than the width of the guide track and when the cam handle is in a closed position the distance between the rolling devices is approximately equal to the width of the guide track.