The Grilling
In the United States, the experiment of grilling was tried in 1867, where tiny squares were embossed into the paper after the stamp was printed, the idea being that this would break up the paper fibers and let more ink be absorbed into the paper. How does this avoid reuse? But this also made the stamps more prone to tearing, and grilling was abandoned around 1871. The more unusual types of grills are now among the great rarities of US stamps.
Read more about this topic: Postage Stamp Reuse