I don't think I have ever used one. Like Rob said, I just use my eyes and make sure its centered. If the trans goes on, your good. Once the slave is hookep up, I just press on the clutch once to let the disk sit on the input shaft freely.
1G DSM: 1000+ AWHP, 9.2@162.83 MPH Evo X: 746 AWHP, XR9569S pump gas www.dynotuneracing.com