A word, such as "SAFE", is ghost engraved on a special tamper resistant material that, once signed or printed on, cannot be easily altered. If an attempt is made to remove or lift the "SAFE" strip, the words "void" will appear in the background. If they can use it for Credit Cards then why not for checks? This feature works especially well in the amount field when amount alteration is the concern. Verification is accomplished by tipping to light.