Sign-stealing by MLB teams is becoming ever more sophisticated, and some clubs are responding by making their own signs from catchers to pitchers difficult to decipher. The Nationals took their countermeasures to an extreme in this year's World Series vs. the Astros.
Per The Washington Post, Nats coaches worked out a plan before the best-of-seven Fall Classic to keep Houston from, legally or otherwise, picking up signs and then relaying them to hitters. The product was a complex set of signals that were used for every pitch, not just with runners on second base.
The main setup, as reported by the Post's Barry Svrluga, who spoke to Nationals pitching coach Paul Menhart and reliever Sean Doolittle:
First, each pitcher had to have his own set of signs, and catchers Yan Gomes and Kurt Suzuki had to be familiar with each one. So the staff printed out cards with the codes and had them laminated.