Ah, yes, there are reasons for that. The moving Object needs to be solid. Imagine a glass panel from a sunroof of a car. If you open the roof, the glass slides along the shape of the car silhouette but it keeps it shape. In my case the object is mounted with two bearings in a rail and follows it. I hope the Sketch helps to understand the challenge. Red is the solid object, green are the bearings aka the rolls and black is the rail.