Pressure release valve.

Use Allen wrench to simply open the long screw to take the two pieces apart. Then, insert them back together by placing one piece from inside while the other piece from the outside followed by tightening the screw. When done, then only place the WARNING stickers once the valve is in the closed position. This way, when closed, the sticker will face up. NOTE: Punch the center half-circle sticker pieces from both stickers. Then affix each sticker on each circular black plastic surface in a way where the air-release holes perfectly align with the sticker paper punched-out half-circle without any obstructions.