If you will look at the picture as it sits the top jaws have a V cut in them. You put a small flat metal in the bottom jaws held in place with the screws so it will sit flat on the bench. Open the jaws up enough that you can lay the pivots in the V. Give it a spin and you will be able to see the high and low of the arbor. I generally use this for the initial straightening but double check with my lathe. Chuck up the pivot in the lathe headstock and put a center point in the tailstock. Spin the wheel by hand to check if it is dead on.
It is easy to use and self explanatory. I use the plate spreader especially when setting up the strike sequence on antique clocks to get all the pins correctly set. Makes it so much easier to do.
