Building square

There isn’t enough information there for me to grasp what you’re dealing with, Pat. Pictures? Illustrations of some kind? Overall dimensions? Does it sit on the floor? Etc.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

Take the shelving unit and put a bar clamp on the diagonal that’s 5/16 out and clamp it to square. Hopefully you can remove the upper and lower rails first.

Oops, after reading Patron’s advice I’m thinking the place where you want to install said unit is out 5/16”. No?
That’s a different can of worms.
Build it in place.
Follow Patron’s advice.

If I understand the situation correctly, again.

more pics is good

build it square
if the wall is out
add a scribe molding there
(or shim the base)
it can be removed later

and the cab is still square

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle

What patron says. Scribe molding can be your best friend. – lol

-- Adversity doesn't build character...................it reveals it.

I have to agree with David, I built a bookshelf that was square where i used to live, when we bought our new house 2 years ago the ceiling dipped in the other direction. The bookshelf is square but looks out of whack, once I create a new molding it will look as good as it did in its old spot.

-- Martin ....always count the number of fingers you have before, and after using the saw.

Guys, I would love to show a pic but nothing is build yet. This unit will be 37 3/4” wide by 40 1/8” tall at the shortest side and on the left side its 5/16 taller because of a sloping floor. I like the idea of shimming but don’t want the shims to show. Like Patron suggested I could use a small moulding to cover it. Might finish the complete piece first and then add the scribe moulding with some 23 gauge pin nails only, this way down the road could remove that if need be finish will be intact.

This will be to hold my MRR magazines and will sit under an installed perfectly level tabletop for the RR to ride on. Hope this helps a little with the layout.

-- ***Pat*** Rookie woodworker looking for an education!!!