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 <WSD>slab</WSD> flooring and someone , clasping him by the arm , whispered , `` I want a word with you , please '' . 
Meaning of the word marked with <WSD> tags:  block consisting of a thick piece of something