The benchmark Sensex and Nifty indices are likely to open gap-up on March 1 as trends in the GIFT Nifty indicate a strong start for the broader index with a gain of 203 points. In a highly volatile session on February F&O expiry day, the Indian benchmarks ended with marginal gains with the Nifty finishing around 22,000 level. At close on February 29, the Sensex was up 195.42 points.