If you have been trying to figure out the 0.02" inaccuracy of the BitZero v2 (as depicted in this now closed topic: Bitzero V2 Not accurate - #17 by CNCj) I have a simple solution that does not require a jig:
Zero the Z axis as normal (place the Bitzero entirely on the surface to be zeroed out (doesn’t work for wasteboard). Then I place a machinist block on top of the surface. The block is made from metal and measures 1x2x3". I place it for 1" thickness and place the bitzero right behind it - touching the surface of the block. I then move the router. head until I touch the block and see the light turn red. Now I know where 1" really is, and can lower the head by the offset. In my case it is 0.019".so I move the head away from the surface being measured, go to z=0, move the head 0.019" down and now I have an accurate z=0.
The reason you can do this on the wasteboard is because you would have to dig into it. Actually you could use the space between boards (where the rails are) to make that move…