It is of importance that the office should be immediately informed of any renting premises which are vacant, and each collector should make a report of these every day. It is a common practice to keep a list of vacant houses on a sheet or slate, and trust to no other record. If a large number of houses are cared for, some precaution must be taken to prevent the possibility of premises being overlooked. This depends largely on the rent bookkeeper, who should also act as a rental credit man. The board described in Section 37, and originally designed from a hotel room board, has been found very serviceable for this purpose.