You can select reference components for components mated for linearly coupled motion.
The assembly origin or ground is the default point of reference for the measurement of linear displacement of components mated with linear couplers. When you select a reference component for a mated component in a linear/linear coupler mate, the linear displacement of the mated component is measured with respect to the selected reference component, rather than ground.
When required, select reference components when you specify linear/linear coupler mates in the Mates PropertyManager.