OK,
We have several wonder bars on the wall. They're not all the same.
One has a 5/8ths square hole in it on the flatter end, cut with a dremmel and cut off wheel.
The hole centers back just far enough from the nail pulling fork that you push the fork under the rocker nut and press down on the valve spring. Lay a magnet over the hole, and remove the keepers.
Of course it should go without saying that the cylinder is charged....By the way, a charged hole is the best diagnostic tool I ever discovered.
Duntov