I have some ply where the grain is going the wrong way,
so it's too short in the direction I need...

I usually end up with scrap plywood offcuts like that when I finish a
project. I store them away and usually find a use for them where I can cut
them into smaller pieces with the grain running the right direction.

Then, I buy a new sheet for the current project, and add any cutoffs to my
collection.

On the other hand, if it's not located in a visible area, or carrying a
load like shelving, the grain direction isn't all that critical. I've used
scrap plywood as drawer bottoms with the grain going the wrong direction,
no problems at all. I've also used incorrectly oriented plywood where it's
hidden by drawers or other parts of the project.

Anthony Watson
www.watsondiy.com
www.mountainsoftware.com