Tap: should it lock? Mine doesn't.

I'm using a TAP appliance, and I noticed that I can move my lower jaw forward and back with appliance in place (even after inserting metal tab into slot). Out of my mouth, I can see that there is a lot of play, 3 or 4mm or so, where the lower section can move forward and back.

Is this supposed to lock? I'm afraid that the purpose will be defeated if I pull my lower jaw back while I'm sleeping.

Again, I realize that the metal tab goes into the slot, but that doesn't keep the front and back pieces locked.

There should be “some” play so you can move your teeth when you grind.

Also, check your adjustment before bed and in morning. I am losing a half turn by morning.

I used to have phlegm in the morning before using the Tap. That’s almost gone after starting adjustment. I am on three full turns.