The doors of the Point Reyes post office will be locked at night, thanks to persistent problems with people sleeping, defecating and smoking in the lobby. Postmaster Lanhua Zhou said the final straw came last week when she found poop on the walls and a smoldering fire in the wood chips outside. The change is posted as temporary, but Ms. Zhou says she is only waiting for authorization to make it permanent. Boxes will be inaccessible from 5:30 p.m. to 7 a.m. on weekdays and from 5:30 p.m. on Saturday until Monday morning.