What is an example of a voting requirement that was used to prevent African Americans from voting during the jim crow laws

In the Jim Crow South, a literacy test was one of the tools used to prevent African-Americans from voting.

It was imposed on anyone who could not "prove" a fifth-grad education. While this might not seem too harsh, it was frequently only given to the people that the election officials did not want to vote. It was also brutally hard (look it up!).