I have a toilet seat that has little by little, become very loose. I have searched the internet and found I had to tighten the two twisting things underneath the toilet bowl, in the back.
They are twisted / welded shut and always have been. If I manually jiggle the toilet seat, it feels as though the heads of the screws in the backs are firm, but the toilet itself is not locked to them. The toilet seat itself won't come off and only wobbles on the horizontal plane.