I mentioned something called "switch backs" on page 1. The term is borrowed from trader Tim Morge. Basic s/r states that when a support or resistance level is broken, that level, then becomes the opposite of what it used to be. When price comes back up/down to that level, price may see buyers/sellers.
Here is an example on FAS. That blue line where price had the breakout, WOULD have been double bottom support, should the price held up, but it didnt. That blue line then becomes resistance as you can see price testing it.