What we want to achieve with an ideal and optimal deadlift lockout is when you feel the bar reach the bottom of your knee, then the athlete will begin driving the hips through to meet the bar at lockout. So as the bar rises, the hip comes forward and they meet at the top. Rather than pulling the bar up and back into the hip, we want the bar to move in a straight line throughout the lift.
When you get to [your knees] pull it in and squeeze your butt. So you're keeping [the bar] closer [to your body] so it changes how long you got to pull it and it doesn't keep your hips high.