First of all, I wish to thank all of you who continuously respond to my (dumb) questions with valuable information. With the skill levels of most of you, I unfortunately don't often have anything you don't already know to offer in return.
I bought two sheets of 3/4 inch Birch plywood and soon discovered they were not square. When cutting down, I can get two sides parallel with no problem, but have difficulty getting two adjacent sides square.
The T-square I got from the big box is worst than the sheet of plywood. Granted, it was intended for cutting wall board; accurate enough for it's intended purpose but not accurate enough to get a perfect 90 degree. Are there any good (perfectly accurate) T-squares that can be used to obtain good square corners?
What methods do you use to square a piece of plywood. Is a cross cut sled my answer? How big a panel will a cross cut sled safely handle? What about larger panels? The panel I cut is 39" x 24", seems to me that would be too large for a cross cut sled.
Again, my thanks to all who take the time to help out by passing their skills and experiences along to others, hopefully some day soon I will develop some skills to start helping others in return.