Law of Selective Gravity

An object will fall so as to do the most damage.

Jennings' Corollary: The chance of the bread falling with the butter side down is directly proportional to the value of the carpet.

Murphy's Corollary

Left to themselves, things tend to go from bad to worse.

Murphy's Second Corollary

It is impossible to make anything foolproof because fools are so ingenious

de la Lastra's Law

After the last of 16 mounting screws has been removed from an access cover, it will be discovered that the wrong access cover has been removed.

Corollary:

After an access cover has been secured by 16 hold-down screws, it will be discovered that the gasket has been omitted.