Rubber Floor

What is nippled rubber floor mat ?

I came across the expression in the novel.
It described the floor mat inside the bus.
What is “nippled rubber”? Bumpy rubber?

Slightly bumpy or otherwise textured rubber that has a better grip than smooth rubber. Ideal for floor mats and things.

Budweiser (Rubber floor) advert

POLYFLOR STUDDED RUBBER 3mm X 500mm X 500mm FLOOR TILES £28.14

Grey Rubber Floor tiles – Artigo BS Classic G805 £20.00

floor covering garage shop rubber tile dance marquee £5.00