Problem scenario
The toilet seat keeps falling down. You cannot clean the toilet with one hand. How do you keep the toilet seat up?
Possible Solution #1
Look at the back of the seat. There may be two plastic covers of bolts that attach the seat to the toilet. Lift the covers, and then look to see if they are parallel and securely fastened.
You may need to loosen one or both bolts, adjust the seat, and test if the seat won't fall. Then tighten the bolts and close the covers.
Possible Solution #2
See this posting or watch this one-minute video.