Holmes and Watson were investigating the office of the League of the Red-Headed Men. Wilson describes it as furnished with nothing but several wooden chairs and a deal table. (A deal table is a crude table made of wooden planks, somewhat like a picnic table.) The description of the room shows it was cheaply and scantily furnished.
Nevertheless, Wilson takes the four-pound-a-week, four-hour-a-day job in this office copying out the Encyclopedia Britannica because it is such a high-paying job for very easy work. He is locked into the office for the duration of his shift and told he will be fired if he leaves. He has copied out most of A in the encyclopedia and is looking forward to B when suddenly he finds a sign on the office door saying that the League is dissolved.