The reasoning behind drawing support and resistance levels on price is easily explained by referring to these levels as areas of supply and demand. So, what’s the explanation for drawing S&R levels on oscillators and indicators, such as on balance volume?
Thanks.
Your question is not clear. You don’t draw support or resistance lines when you use oscillators, on balance volume or other indicators like the ones you mentioned. Indicators as the name suggests indicate. Trend indicators indicate trends, momentum indicators look at momentum, cycle indicators indicate start or end of different market cycles. There are support and resistance indicators that will show support and resistance areas.
No matter what the indicator, in my opinion they should be used to confirm your analysis. When traders first start trading a great way to use indicators to show you something and then you analyze how the indicator came to that conclusion. Or look at 3 or 4 different indicators that display the same thing. For example for support and resistance, you could use different indicators that all are meant to illustrate support and resistance, and figure out how they came to that conclusion as well draw your support and resistance lines to see how you measure up.
Indicators are like any tool you can use, they are only as good as the person using them. Remember this, How you start out is not how you have to finish. When I started I used several indicators for trend, momentum, cycle, support and resistance. Today I use Support, Resistance and one or two others when I need them. Hope that helps
Gp
Okay I got you. The lines in the OBV are not support or resistance, they are % levels which show over sold and overbought areas. So if the obv line crosses 80% line that’s giving you the signal to go short, the bottom is showing a long signal. Some times traders use one line 50% above you go long below you go short. Other traders use the reading on the obv to confirm signals on the particular time frame.
Example the obv indicator below is showing an 80% 50% and 20%
Knocks,
Take a look and read through the Stockcharts web page on the OBV indicator. They show some good examples of drawing trend lines on the indicator, and explain why. 
link to On Balance Volume (OBV) [ChartSchool]
Also, take a look at the info on the other tech indicators listed in the ChartSchool, you’ll see many examples of drawing trend lines on indicators, especially when plotting divergences.
