plain as day
Also, plain as the nose on your face. Very obvious, quite clear, as in It's plain as day that they must sell their house before they can buy another, or It's plain as the nose on your face that she's lying. These similes have largely replaced the earlier plain as a packstaff or pikestaff, from the mid-1500s, alluding to the stick on which a peddler carried his wares over his shoulder. The first term, from the late 1800s, is probably a shortening of plain as the sun at midday; the variant dates from the late 1600s.