Handicapped accessible sidewalk ramps (are) made mostly of concrete but with a nubbed, fiberglass composite insert. The slope of the ramp is designed to aid people with mobility issues. The texture of these nubs – officially called truncated domes – alerts the visually impaired that they are are approaching a crosswalk.
These are ADA-mandated, and also are referred to as warning pads or truncated dome pavers. You can see two of them here.
But the one on the southwest corner of 5th & Elm is gone.
Look -- here it is, tossed over the fence.
There's a metaphor luring here somewhere. I just can't put my finger on it.