Holmes once again in this story shows an uncanny knack for being able to tell a lot about a person and his background from merely looking at their appearance and their dress. At the beginning of the story, after Watson tries to look at Jabez Wilson and deduce what he can from it, Holmes then steps in and reveals to them both what he can tell from Wilson's appearance:
Sherlock Holmes's quick eye took in my occupation, and he shook his head with a smile as he noticed my questioning glances. "Beyond the obvious facts that he has at some time done manual labour, that he takes snuff, that he is a Freemason, that he has been in China, and that he has done a considerable amount of writing lately, I can deduce nothing else."
Holmes goes on to explain on what he bases these conclusions, and it is clear that they are grounded on tiny bits of visual information that are ignored or not seen by others, such as Watson, who do not see the value in the tiny minutiae that form the bedrock of Holmes' detective abilities. What is ignored by others is of profound importance, such as the way in which Wilson's right hand is slightly larger than the left, because of the manual labour he has done with it.