size(1000,600);

stroke(127);

// These are the vertical guidelines
for (int x=0; x <= width; x += 100)
  for (int y=0; y <= height; y += 10)
    line(x, y, x, y+5);

// These are the horizontal guidelines
for (int y=0; y <= height; y += 100)
  for (int x=0; x <= width; x += 10)
    line(x, y, x+5, y);