How did grandfather cluases keep free black men from voting after the civil war?

Grandfather clauses were legal provisions that allowed individuals to vote only if their grandfathers had been eligible to vote before the Civil War, effectively exempting white voters from literacy tests and other restrictions. This discriminatory practice disenfranchised many free Black men whose ancestors had been enslaved and denied the right to vote. As a result, grandfather clauses reinforced racial inequality and maintained white supremacy in the electoral process during the Reconstruction era and beyond.