If I understand you correctly, this movement is the opposite of what I know as a "piston hip," where you are locking the hips UP on each side.

With hip locks down, you release your right knee so that your right hip is going down (hence your left knee is straightening slightly and your left hip is going up, but you're focusing your attention on the right) and you lock the glute on the opposite side to give it a sharp lock down.

It's actually the SAME movement physiologically as if you were sending your left hip up, BUT you are emphasizing the hip going downward. Concentrate on making the knee release and the glute lock simultaneous and equally sharp, and it will help put the focus where you want it.

Another thing that might help a bit is to think of where the movement goes. I'll try (eep) to explain without being there to demo (sigh! darn cyberspace) - when you do hip hits (or what others may call a "bump") the energy of the movement definitely goes "out". This "out" can be to the side, forward, or back, but your hip definitely travels away from your body. If you do a hip hit (right now! as you read this!) you'll notice that the weight goes onto the leg that's hitting the hip out. There's a definite weight shift and, in my case when I do them, so much so that I wind up with all the weight on my foot and can easily left the non-hitting leg. You're literally transfering the weight onto the leg/side that's hitting out, causing the whole movement to move out and away from the body.

The hip lock down is a bit different. This movement is not occurring out away from the body but is, rather, more to keep it "underneath" you. So the goal is to keep the weight fairly centered so that the movement does not get away from you. You'll find that, when you do this properly, the weight is not swinging out to one side and the shift in weight is much more subtle. You'll feel weight going onto the foot/leg that's dropping down, but you'll notice that, in general, the weight stays firmly centered in your feet (rather than shifting substantially to one side).

Think of having a tight glass tube around your body. Your hip hit would travel out burst out through the tube (or bump up against the wall of it). But, a hip lock down or a lift would occur just inside the tube's walls. This visualization might help you get the image of where the hip goes, if the technicality of "do X with the glute" doesn't work for ya ;) Practice doing it slowly, first - sometimes trying to add in the glute right off the back is difficult if the glute control is not yet developed. Instead, work on imagining that you're driving the hip bones DOWN into the floor.

Also, try to do it very slowly and really feel the way the hip moves downward. Watch your posture - be sure to keep the knees spongey and the pelvis tilted. Be kind to yourself - don't expect a grand movement if you're just learning this and have not yet developed a high degree of muscle movement (it will come, I promise!). Practice slow and steady, get the feel of the movement into your muscle memory, and then add the sharpness of the lock.

Oh, and...

When you're walking with the hip drops, you must remember to raise the hip slightly as you lift your foot to step. You step down and send the hip down at the same time. If you don't raise the hip slightly on the "and" count, it's more difficult to drop while walking.

Okay, it's possible this has already been answered and I missed it in re-reading this thread. If so, my apologies for asking the same question. Please just direct me to the appropriate part of the thread if this is the case. If not, please answer...

What is the difference between a hip down and a hip lock down?

For me, a hip down is just as (shoot, forgot the name) the really nice lady described it in the beginning part of this thread. Pushing the hip down, rather than out to the side (hip bump). Where does the lock part come in? Is that the glute squeeze on the opposite side?

Well here we go with more confusion. I was taught that hip lock is like a pelvic tilt. locking the hips forward with a contraction in the lower back and locking it back by contracting in the front. Wish we had a standard language.