Believe It Or Not, These Aren't Actually Design Flaws

The Lines on a Red Solo Cup

The lines on a solo cup are actually meant for measuring your drinks. The top line is for 12 ounces of beer, the middle line is for 5 ounces of wine, and the bottom line is for one ounce of liquor. That way you can have fun and easily keep track of your booze.

The Hole in a Pen Cap

You'd think the hole in a pen cap serves no purpose, but it's actually a safety precaution. For whatever reason, people love to chew their pen caps. If a child happened to swallow one, the hole in the top allows air to circulate to prevent choking.