How is Douglas treated during the first six months that he works for Covey?

Douglass recalls that his hardest experiences during his time as a slave were his first six months with Covey.

Douglass was sent to live with Mr. Edward Covey in January 1833, and found himself a field hand for the first time in his life. He was not prepared for this, and he was certainly not prepared for the brutal whipping he received from his new master. He was given the task of taken an unbroken team of oxen to get a load of firewood, but the stubbornness of the creatures led to two near-death experiences for the young Douglass. Covey would listen to none of his explanations, however, and told Douglass he would show him how "to trifle away my time, and break gates." Douglass tried to refuse but to no avail, and was whipped several times for minor offenses over the next few months.

One thing that made Covey different was that he worked with his hands and was quite skilled at it. He knew what hard work meant. He tried to surprise and ambush his slaves, hiding and waiting for them so they never knew when to expect him. His whole life was devoted to duplicity, devoted to "planning and perpetrating the grossest deceptions." He also conceived of himself as religious, but of course this was very hypocritical.

Douglass's worst experiences in the bonds of servitude were his first six months with Covey. He was worked nearly to death in all weathers. He felt broken in mind, body, and spirit. Even his intellect languished and his spark of life extinguished. He considered taking his life but both hope and fear prevented him from doing so.

What does Covey do that makes the slaves feel that he is always present?