I am trying to set up a solenoid assembly so that I can actuate the solenoid and have the linkages respond by moving in a realistic manner.  I am encountering problems when I try to set up the imaginary "hinges" or rotation points in my assembly.

The way that I would like to accomplish this is by creating reference axes that are fixed in space and having the linkage holes mated to them with concentric mates.  The problem is that I cannot find any way to create those reference axes without having selectable geometry to define them.  I tried creating reference points (which I could use to define the axes) but had the same problem.  Even if I create a sketch in the assembly with the axis through-points defined, I apparently cannot use a sketch to define reference geometry.

Does anyone know of any way to do this?  I realize that I could create a part for the purpose of defining the needed geometry, then just hide it my assembly, but it doesn't seem like that should be necessary.

Thanks!