If you sell your existing shares from your portfolio then you will receive 100% margin against those shares on T+1 instead of same day due to regulatory guidelines. 

But If you sell your already pledged shares, you will receive 80% of the sell value immediately on the same day and the remaining 20% is credited in your account on T+1 day.

You can pledge your shares by clicking on Pledge Shares for more margin under Funds tab.,

Please note that the pledging and un-pledging charges are Rs. 20 per scrip (Number of shares is not included in this calculation). 

For example: If you pledge 10 quantity of scrip ABC and 5 quantity of scrip XYZ stocks then Rs. 40 will be chargeable.