I made a newbie mistake. I'm building a "built-in" set of shelves out
of birch plywood -resting them on cleats nailed to the wall. The
shelves are going in a little aclove and are spanning the entire
distance. Unfortunately when I measured the space for the shelves I
measured the space along the wall where the back of the shelves would
be. However, now that we are installing the finished and urethaned
shelves I notice that the walls aren't entirely straight and the front
of the shelf is just a little to big to fit in nicely - maybe less than
1/8" too big.

What's the best way to shave down the edge of the plywood to make it
fit? The urethane is (mostly) not on the sides -just the top and
bottom. Should I use a file, finish sander with low grit, hand plane or
something else? I've got 5 shelves to do this to.

BTW, no tablesaw - I built these using only a circular saw and router,
so no fancy TS solutions please.

Thanks!

-Bob