MGN Rail jig

When I decided to replace wheels on my printer, I thought Y was a good starting point.
I prefer to install 2 rails to have more stable bed.
So the question was how to set the two rails flat and parallel each other?

I prepare this jig, 2 of them allow to set a rail exactly in position. it can be used on 20x20 or 40x40.

I installed them easily and do not need any further adjustment just tight and print