You can use SMA's to define "The River." The river is a term used in trending markets to show when the price is pulling back and ready to launch to a higher high or a lower low. In the example I am showing you below, the river is defined by the 20 and 40 SMAs . The 20 in black and 40 in green. Notice how often price tends to pull back into the river before making a new high (in this case it is a high because of an up-trend, but it is also true in a downtrend when it is making new lows).
You can see that many of the pull-backs come in between the 20 and the 40 before reverting back into the trend. There are between the 20 and the 40 is referred to as "The River". The river can be used to help identify areas to get back into the market during trending periods.
This strategy is taken from our TSG Blog site - Using Simple Moving Averages to Clarify the Forex Market