not be able to hit the broad side of a barn

verb1

1. •
   (informal) To have very poor aim, such as while using firearms or in sports.

   • No, I am really not good at batting in baseball. I cannot hit the broad side of a barn, really.
   • The new recruit is absolutely worthless with a rifle. Blimey, she wouldn't be able to hit the broad side of a barn if I asked her to.