The engine evaluates each rule from right to left, starting from the rightmost selector (called the "key") and moving through each selector until it finds a match or discards the rule.

If you walk clockwise, you will see that the surface is to your left or use the right-hand rule.

In these cases, food is often offered communally, which is why it's important to wash your hands before eating and observe the right-hand-is-for-eating and the left-hand-is-for-other-duties rule.