Tim, I found another one by Max.
The switches used in a two switch system are called three way because each
switch has three terminals. Let's call the terminals A, B, and C. When the
switch is in one position terminal A is connected to terminal B. When the
switch is in the other position A is connected to C. B and C are never
connected together. At the bottom of the stairs terminal A goes to the hot
side of the line. Terminals B and C of the bottom switch go to terminals B
and C of the switch at the top of the stairs. Terminal A of the top switch
goes to the hot side of the light fixture. According to national electrical
code the threads of a light socket are supposed to go to the neutral and the
bottom contact to the hot. Hope this helps.
Max.
