Who is Stradlater, what does he look like, and why does Holden refer to him as a "secret slob"?
Ward Stradlater is Holden's roommate at Pencey Prep. Stradlater is a lady's man, and jock, and boastful about his sexual prowess with the ladies. Stradlater is going on a date with Jane, who is a childhood friend of Holden's. He obviously has a strong emotional attachment to her, based on his reaction to Stradlater mentioning her name. Stradlater uses Holden for his jacket (which Holden is afraid Ward will stretch out with the broad shoulders) and to write his descriptive essay while he (Ward) is out with Jane.
Holden calls Stradlater a secret slob because, to the outside world, Stradlater looks great. However, Holden notices that he doesn't take great care of the small, personal items. Holden notices that Stradlater shaves with a dirty, gross razor. This is one of the first glimpses the audience gets of Holden's cynical, critical nature.
Ward Stradlater is Holden's roommate at Pencey Prep. Although Stradlater is good looking, Holden thinks he's is a slob because he shaves with a dirty razor. He's also careless of other people's feelings. When he's going out of a date with Jane, a girl Holden really likes, Stradlater treats the date like it's another sexual conquest. He then has the audacity to ask Holden to write an essay for him. Holden complies but writes the essay about his own brother's baseball mitt, not about a room or house, the assigned topic. Stradlater and Holden have a fight over the composition, which is probably just as much about Stadlater's date with Jane as it is the essay.
Stradlater is Holden's roommate who also represents the stereotypical jock. He is sporty and very handsome yet dumb at the same time. The first interaction we see of him and Holden reveals that he is a lady's man and also a lazy student who doesnt do his own homework. The reason Holden called him a secret slob is because he seems slick and clean on the outside but in reality he is dirty, or as Holden described it "a slob" because he uses a dirty razor.