Here's an example on options. Let's say it's trading at Rs. 100 (the premium price) and you want to place a cover order with a stop-loss at Rs. 90. The margin required for this trade is (Rs. 100 - Rs. 90) * 50 = Rs. 500. Without the cover order, the margin required would have been Rs. 100 * 50 = Rs. 5,000.
Usually the broker has a "safety" or "reserve" factor on the cover order margin. If a broker sets that "safety" factor to 2X, then instead of Rs. 500 for margin, it would be Rs. 1,000.