Wouldn't know (something) if (one) fell over one phrase informal
Used to imply that someone would not realize something even though it's obvious and clear
It's regrettable that parents wouldn't know their children who can be geniuses if they fell over one.
They are not experts in appraising treasures, so they wouldn't have known about these fake antiques if they fell over one.
To give no interest or attention to someone or something; to believe that something isn't important
To not care in any way about something or someone
1.To do nothing, ignore the problem or situation needing to be coped with
2.To not want to applaud