Section 11. Every register shall keep in his registry all books, records, deeds and papers belonging thereto, and shall keep the office open a fixed number of hours daily on days other than Saturdays, Sundays and holidays, for receiving and recording papers, except that, if the convenience of the public so requires, a register may keep his registry open on any Saturday, not a legal holiday, for said purposes during such hours as he may determine. Office hours heretofore fixed in the respective counties shall continue until changed by order of the county commissioners. Notice thereof shall be given by posting the same in conspicuous places upon or near the entrance door and upon the walls or counters in each registry. The provisions of section nine of chapter four shall apply in the case of the closing of a registry on any Saturday to the same extent as if such Saturday were a legal holiday.