Forklifts are categorised according to the space in which they work. There are a number of different aisle types in common use. Due to a number of factors, standard forklifts can only work in some of these environments.
Lift trucks are designated according to the aisle type in which they are designed to work. There are three aisle width types in common use -- wide aisles (greater than 11 feet), narrow aisles (8 to 10 feet), and very narrow aisles (smaller than 6 feet).
Aisle types are determined with a number of factors in mind. The most important factors are the size of the truck in question, the turn radius of the truck and the size of the loads the truck can carry.
Standard forklifts, or counterbalanced sit-down lift trucks, fall into the "wide aisle" category. They are designed to work only in aisles that are greater than 11 feet wide. If the aisle is any smaller, the forklift is unable to turn.