Rectangles are areas of indecision of market players and usually price movement continue in initial price movement. Rectangles look like flags, but parallel lines are horizontal, not slanted like flags. Studies said that those formation (chart patterns) are very reliable. Supply and Demand are balanced, this is the reason that those horizontal lines are tested several times – their highest and lowest values.
If you are an aggressive trader you can short 2 or 3 bars after which price found support and to put stop 5-10 pips above that bar. You can face high risk, because price can turned back and break that support line, and this pattern will no longer be valid, but reward is very good.
If you are conservative trader you can wait the price to break the resistance line and then go for long. You must place your stop loss order 5-10 above bar that reached support line.