can’t hit the broad side of a barn

Describing a person with very poor aim. The term is thought to have originated in the mid-nineteenth century in the military. It was often repeated in the early twentieth century, when it was applied to untalented baseball pitchers who could not throw the ball over the plate with any consistency. The “broad side” in this expression also suggests the old naval meaning of broadside, that is, a simultaneous discharge of all the guns on one side of a warship. However, there are numerous variants (the inside of a barn, the right side of a barn with a shotgun, and so on) that suggest the term may also have been rural in origin.