Most people know that the numbers on opposite faces of a six-sided die add up to 7. Fewer know that these come in two different forms: left-handed and right-handed. You can tell which is which by standing the die with its 1 uppermost, so you can see the 2 and the 3. On a left-handed die, the numbers read 1 2 3 in anticlockwise order; on a right-handed die, they read 1 2 3 in clockwise order. Most dice are left-handed, but here's a picture of a right-handed one:
My younger daughter got a die in a game inside a Christmas cracker. I asked whether it was left-handed or right-handed, then launched into the above explanation when she said she didn't know.
Then, she showed me the die:
Damned smart-arse kids!