Mail handlers and distribution clerks may become bored with the routine of moving and sorting mail. Many work at night or on weekends because most large post offices process mail around the clock, and the largest volume of mail is sorted during the evening and night shifts. Window clerks, on the other hand, have a greater variety of duties, frequent contact with the public, and rarely have to work at night. However, they may have to deal with upset customers, and they are held accountable for the assigned stock of stamps and for postal funds. Most carriers begin work early in the morning, in some cases as early as 4 a.m. if they have routes in the business district.
Carriers spend most of their time outdoors, and deliver mail in all kinds of weather.
Even those who drive often must walk when making deliveries and must lift heavy sacks of parcel post items when loading their vehicles. In addition, carriers always must be cautious of potential hazards on their routes.