Mumbai: Followed by the cases of remarkable prices movements before the stock's inclusion or exclusion in the trade to trade (T-T) group, the Bombay Stock Exchange (BSE) and the National Stock Exchange (NSE) have decided to chalk out some rules for putting scrips under surveillance, reports Palak Shah of Business Standard. As the stocks lure a circuit filter of five percent and the delivery is compulsory, punting is strongly discouraged under the T-T category. Whenever unusual price movement is seen, scrips are often put under this category. The T-T category was introduced immediately after the Ketan Parekh scam which happened in 2001. But the details were not so well laid out. "Rules regarding inclusion and exclusion of stocks in the T-T group are vague. Nobody questioned why a particular stock was put under surveillance in the first place," said a broker. The recent sharp rise and fall in the price of Ramswarup Industries is one of the examples of price manipulation through leakage of information. From a high of 119 on July 23, the stock fell 30 percent to 82.9 on August 17 when it was included in the T-T category.