Lower Berth Quota is only for male 60 yrs & above and female 45 yrs & above passangers who travel alone.There is no option to mention it at the time of booking.There is no quota code which the reservation clerk has to enter at the time of booking as is the case for all othe quota.the system automatically confirm the seat if it is avilable under this quota. Even if two eligible people want to book under this quota they cannot book the on a single form. Only eligible people who travel alone are given these berth