Mate the front plane of the saddle to the front plane of the assembly.
In the flyout FeatureManager design tree, select
the following for Entities to Mate
:
Front Plane of the assembly mill
Front Plane of the component saddle
Do not accept the coincident mate. Instead, add a distance mate.
In the PropertyManager, under Standard Mates:
Click Distance
.
Type 250 for Distance and press Enter.
To see how you can flip the direction of the dimension, select and then clear Flip Dimension several times.
Position the saddle near the center of the knee.

Click
twice, to accept the mate
and close the PropertyManager.
The positions of the saddle and table are fully defined. In the FeatureManager design tree, the prefix (-) no longer appears for saddle and table.