Curbstone
A curb (American English), or kerb (British English; see spelling differences), is the edge where a raised sidewalk (pavement in British English) or road median/central reservation meets a street or other roadway.
Wikipedia
Kerbstone (noun)
A paving stone that forms part of a kerb
Curbstone (noun)
alternative spelling of kerbstone|from=US
Wiktionary
Kerbstone (noun)
a long, narrow stone or concrete block, laid end to end with others to form a kerb.
Curbstone (noun)
variant spelling of kerbstone
Curbstone (noun)
unqualified; amateur
“curbstone commentators”
Oxford Dictionary