What are these knobs on my Thetford swivel cassette toilet? (In an ALiner Evolution 15 LG)

* The blue knob opens and closes the anti-stink flap

* The blue button lets air in while dumping to prevent glugging

* The large grey lid is pushed open when cassette is inserted

But what are the grey rotary knobs? There are 2 and they have Lock / Unlock icons next to them.

Thanks in advance

RESOLVED: That tab is an auger brake.

I've got a Husqvarna 1830HV Snow blower (large 2 stage machine.

I split it and replaced the belts, but when I go to close it up something is "funny". See the picture. There is a tab on the arm that holds the auger idler pulley. This is the pulley that is pressed in to the belt to activate the auger/impeller.

When I close the machine this tab hits the impeller pullet (see photo). If a squeeze the handle (activate the idler) it clears the pulley, but when I release the handle the table moves until it hits the pulley.

What am I missing or doing wrong?!?!?