Brutality Enforced by Law, with Corporal Punishments and Financial Rewards.

Under South Carolina's 1740 Negro Act, enacted in the wake of the Stono (or Cato's) Rebellion, enslaved people in Charleston who engaged in buying and selling goods were required to be publicly whipped up to twenty lashes.
Owners were not allowed to permit their enslaved people to wear clothes "above the condition of slaves". Their clothes couldn't be anything "finer, other, or greater value than Negro cloth, duffels, kerseys," etc. and if they were found in finer clothing, the constable, or other persons, could take the finer clothing from them and use it for themselves.
The penalty for teaching an enslaved person to write was 100 pounds.
Because Spain was encouraging slaves to escape to St. Augustine, Florida to undermine and fight against the British, South Carolina authorized rewards for the return of slaves dead or alive:
     --fifty pounds for every gown man slave brought alive;
     --twenty-five pounds for every grown woman or boy slave over twelve;
     --five pounds for every child under the age of twelve;
     --twenty pounds for "every scalp of a grown Negro slave with the two ears";
but if the slave was found south of the St. John's River, the reward was one hundred pounds for live captives, and fifty pounds for the "scalp of every negro with the two ears."
https://en.wikipedia.org/wiki/Stono_Rebellion