From the ORD website:
Our new axle offset plates are an easy and inexpensive way to offset your front or rear leaf-sprung axle forward or back 1/2", 1" or 1-1/2" depending on how they're installed!
Basically they bolt into the bottom of the spring pack like any other leaf but allow you to offset the center pin and adjust axle location.
This can be useful to improve approach/departure angles, help with tire/fender clearance and they can also account for other things that have moved the axle (for example, to account for a shackle flip moving your rear axle forward).
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I just did the 2.5" shackle flip and you can see the rear axle was moved forward and was no longer centered in the wheel well. This bothered me. A 4" flip will move it farther forward.
The 1/4" axle plate will bolt into the spring pack at the very bottom of the spring pack. They give you a very short allen bolt you thread into the center hole. This will go into the hole in the spring perch in the axle. You then use whatever other hole you want to bolt into the spring pack with a new spring pack center pin bolt.
On the ORD website look at the zero rate block. They have instructions on it. It is the same as the axle relocation plate but is 1" thick instead of 1/4" thick.
https://www.offroaddesign.com/1-zero-rate-add-a-leaf-kit-2-1-2-wide.html
At the bottom under "product attachments"