Locking is nothing but freezing the options that you have selected. For example, in Round 1, you select few Colleges and lock them. The seat is allotted based on the choices you have made, merit and preference. If you do not lock your choices by the mentioned time, the system will automatically lock your choices and a seat will be allotted from that list based on merit and preference. Now every Round has its own choice locking. Round 1 choices are not applicable for Round 2. You need to fill fresh choices for Round 2 and mop up round as well. For a complete list of colleges that you may have a shot at, please use our College predictor: https://medicine.careers360.com/neet-college-predictor?icn=QnA&ici=qna_answer