Stackers are storage machines through which operations are carried out for the transportation, lifting and removal of palletized loads from shelving systems. These types of high lifters are mechanical, semi-electric and electric. Mechanical and semi-electric stackers have relatively more limited functions in terms of working height. Electric stackers have a lifting capacity of up to 2000 kg and a lifting height of up to 5.40 mm. They are used indoors with flat and solid floor surfaces, with narrow work corridors. Stackers are maneuverable and easy-to-use machines, but they require a certificate of training. Most are manually operated, with or without a driver platform.