Razors..
If you go against the pattern of your hair grown, you'll catch bumps as a black man..
When you go against the way your hair grows, you'll cut the hair so close, it'll beneath the surface of your skin..
When it tries to grow back, being that black people hair is course and curly, it may not grow out if the pore.. If it doesn't, it'll push the skin up close to that pore, causing a hair bump..
When you cut with the pattern of your hair growth, your hair will not fall beneath the pore, and can grow back without pushing up any skin..
If you do cut against the grain, you must shave every 3 days to avoid razor bumps..