Cut it.
Check the lines.
The one plywood test that cannot lie.
Plywood is sold on claims. Waterproof, termite proof, lifetime warranty — printed on the sheet, printed on the sticker, repeated at the counter. Almost none of it can be checked by the person paying for it.
One thing can.
Cut the sheet and look at the edge.
The four things to look at
Are the lines straight?
Every layer should run flat and parallel from one end to the other. Waves and dips mean the core is made of short patched pieces.
How long are the gaps?
Small gaps occur in any plywood, including ours — a core can crack, a dry veneer can chip. What matters is length and depth. Short and shallow is a natural defect. Long and deep is a construction choice.
How many layers, and are they even?
Count them. They should be the same thickness top to bottom and the sheet should be symmetrical around the middle.
Is the glue line tight?
Look for a clean dark line, not a gap, not a bubble.
See it side by side
Why it matters where you cannot see it
A patched core is not just untidy. Under a laminate the voids telegraph through as bumps once the adhesive cures. Under load the sheet sags where the core is thin. Under a screw the thread finds a gap and the hardware works loose. None of it shows on the day it is installed. All of it shows in year four.
Do it to ours too
Ask your dealer for an offcut. Cut it. Then cut anything else on the shelf. Put the two edges side by side.