Wilson unrolls his diagram to show a ravaged foot, covered in bruises, corns and bunions, which has been in an ill-fitting shoe.
After a fifteen-mile march, Mainwaring asks the men to have their feet ready for inspection in five minutes, while he and Wilson have a chat in the office.
Mainwaring confides in Wilson that he knows that he is a shy and sensitive man who handles the men quietly and subtly.
Mainwaring and Wilson reappear and inspect the men's feet, and it is revealed that the foot salve is in fact a felt tip pen.
After a few days, it is beginning to take its toll on the platoon, especially Pike, who has a nightmare about marching in bare feet, which are all swollen and blistered.
After his mother storms off, Frank apprises Wilson of a plan to avoid a twenty-mile march on Saturday: swap Mainwaring's boots over for a half a size smaller.
He hobbles into the office, just as Mr Sedgewick arrives with the pair of boots he left for repair last week: a 6½.