In my neighborhood, the sidewalks have these metal buttons embedded in the sidewalk. They look like an oversized Levi’s jeans rivet, are made of copper or brass, and are stamped with “LS 5456.” They are about the size of a dime and appear somewhat randomly. What are they?
— Alan M., San Diego
Those are property markers, embedded in the sidewalks during development. They demarcate the boundaries, usually the corners, of property as measured by professional surveyors. The numbers are the individual surveyor’s identification, because they have to tag every monument they put down during land surveying, regardless of location. The monuments are useful to the city when workers go in and start tearing things up to fix water lines or whatever they’re digging around for, because it lets them know into whose property they’re digging. Occasionally, historical monuments get pegged into the sidewalks, but they’re usually a little bigger and can have more conventional text.