can't hit the (broad) side of a barn

slang Has very poor aim. Boy, you can't hit the broad side of a barn—the net is over here, you know! These guys haven't made a single basket in the last 10 minutes—they just can't hit the side of a barn right now.

Rur. cannot aim something accurately. You're way off. You couldn't hit the broad side of a barn. Please don't try to throw the paper into the wastebasket. You can't hit the side of a barn.

Have very poor aim. For example, That rookie can't hit the broad side of a barn, let alone strike anyone out or, as put in The New Republic (February 19, 1990): "Their missiles couldn't hit the broad side of a barn." This hyperbolic term, dating from the mid-1800s, at first denoted poor marksmanship. Around 1900 it also began to be used in baseball, for a pitcher with poor aim.

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.

A lousy shot. This useful phrase can be applied to baseball pitchers who can't get the ball over the plate, basketball players who miss free throws, golfers whose balls routinely go out of bounds, target shooters and archers who miss the target, and anyone else who can't get it right. Another similar farm-based expression is “couldn't hit a bull's ass with a barn shovel.”