I'm in the final stages of closing the pool. I've blown out the jets and fountain through the skimmer and appropriately plugged them all up.
I've put the gizmo in the skimmer plug where I blew everything out. The skimmer is completely dry until I attempt to blow out the main drain. When I blow out the main drain it works as it should with lots of air and bubbles coming out the drain. But, when we do the lock-routine, it keeps filling back up with water. I am using a cyclone and blowing the air through the hole shown in the picture. I am air-locking the main drain by turning the valve into the off position while my wife simultaneously shuts-down the blower. (Actually, I've tried the valve in several different positions just in case we have it wrong, but no matter what I do it keeps filling back up with water after the blower is turned off. My filter is turned to the closed position. I will mention that my pool pump is a good 90 feet away from the pool if that makes a difference.
Below, shows my skimmer. I am blowing air through the open hole. The other one is where I blew out jets and fountain.

Below is the valve after I presume is the correct position to have it shut-off or locked.
One side of this valve is labelled VAC and I did prove that it blows air out the vac port in side of pool when on. The other side is labelled skimmer.

We're supposed to get a good freeze Sunday night so I'm in a bit of a panic mode now. Thank you so much for your help.
Rob
I've put the gizmo in the skimmer plug where I blew everything out. The skimmer is completely dry until I attempt to blow out the main drain. When I blow out the main drain it works as it should with lots of air and bubbles coming out the drain. But, when we do the lock-routine, it keeps filling back up with water. I am using a cyclone and blowing the air through the hole shown in the picture. I am air-locking the main drain by turning the valve into the off position while my wife simultaneously shuts-down the blower. (Actually, I've tried the valve in several different positions just in case we have it wrong, but no matter what I do it keeps filling back up with water after the blower is turned off. My filter is turned to the closed position. I will mention that my pool pump is a good 90 feet away from the pool if that makes a difference.
Below, shows my skimmer. I am blowing air through the open hole. The other one is where I blew out jets and fountain.

Below is the valve after I presume is the correct position to have it shut-off or locked.
One side of this valve is labelled VAC and I did prove that it blows air out the vac port in side of pool when on. The other side is labelled skimmer.

We're supposed to get a good freeze Sunday night so I'm in a bit of a panic mode now. Thank you so much for your help.
Rob