Sentence:  One day when he attended a war memorial ceremony in Westminster Abbey his view was obstructed by a stout man on his left , his attention turned to the irregular pattern of the rough slab <WSD>flooring</WSD> and someone , clasping him by the arm , whispered , `` I want a word with you , please '' . 
Meaning of the word marked with <WSD> tags:  the inside lower horizontal surface (as of a room, hallway, tent, or other structure)