stringboard

[string-bawrd, -bohrd] /ˈstrɪŋˌbɔrd, -ˌboʊrd/
noun
1.
a board or facing covering the ends of the steps in a staircase.
Origin
1695-1705; string + board
British Dictionary definitions for stringboard

stringboard

/ˈstrɪŋˌbɔːd/
noun
1.
a skirting that covers the ends of the steps in a staircase Also called stringer