I used contact cement. I went to the vet supply aisle at the local farm supply store to get a larger syringe with a larger diameter needle. With the needle on the syringe I sucked up a little contact cement into the syringe and injected the cement deep into the gap between the veneer and backing, then finger-pressed and released several times to spread the cement around in the gap, wiped off the excess cement, if any, let the cement set-up for an hour or so, then clamped the veneer down tight for overnight. I cemented the worst and obvious spots, and have more to do, but none that I have cemented have come loose after three years. If I need to better spread the cement around after the finger-pressing, then I use a toothpick.