Plumb Bob or some layers to get axle square.
On a 4 link rig I make castor adjustments with the upper arms if I can. Pull the bolt out of tge arm you aren't using to make the castor adjustments. Then ounce castor is set adjust the arm to that new location.
It gets rid of the arms fighting eachother as you adjust.
If your upper is true adjustable you can set the angle finder up and watch it change as you adjust the arm.
This stuff gets fun ounce you get the hang if it.
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