Hi P, what about a resistance line that is not horizontal? like a tunnel for example? OCO and OTO still don't cope with that. correct me if i'm wrong.
A non-horizontal line is not a support or resistance, but rather a trendline.
I know that many educators call trendlines 'extensions' or 'special types' of S and R lines, but I personally don't agree with this view, because support and resistance imply a
stop of price movement (rather like a wall, though it can be breached if enough momentum exists), whereas a trend implies price movement, which we all desire to be decisive and long-lasting.
S&R are being used to define entries and exits, trendlines determine the direction of a trade or give us a reason to trade at all, respectively.
In regard of your specific question about the use of OCOs and OTOs: No order type will cope with trendlines, since an entry/exit always needs a precise price value. As mentioned above, trendlines aren't suitable for that.
The idea behind pending orders and the 'exotic' order types is
a) being able to trade without being glued to the screen 24/5 and
b) being able to execute an entry/exit at a precise price level (which in fast-moving markets isn't always possible, since typing in prices costs valuable seconds).
A frequent application of an OCO is the formation of a triangle (doesn't matter which type) on the chart: one knows that a breakout is highly probable, but the direction is often unclear.
One therefore places entry orders above the slope of the lower highs and below the slope of the higher lows. Since one already knows that the price is going to break out, one can just hitch a ride in whatever direction the market moves. Once price moves, one of the two orders will be triggered and the other one will automatically be cancelled without the need to be present to manually cancel a pending order (and it must be cancelled, or you might find yourself hedging without wanting to).
OTOs come in handy as well, but usually require a more elaborate scenario, which I'm too lazy to type up just now.
Cheers,
P.