As we've all been told time and time again, dad knows best. But, we'd like to throw a little revision your way... Dads know a lot. But Grandpas know EVERYTHING. We aren't lying, either. Grandpas really do know everything. Just ask them. They'll tell ya. Because they are proud to be a Grandpa know-it-all! And we think they have earned that title proudly. So, here's to you, Grandpas of the world! This shirt is just for you!