• The term "scissor jack" describes a wide variety of tools that all follow the same principle: using crossed beams to lift something. They do this by acting on the object they are lifting in a diagonal manner; the lift on the right side lifts the object from its left side and vice versa. This allows the user to store the jack when it is not in use (with the diagonal beams flat) and to expand it when it is needed.
  
  

Symmetrical

• The major specification of scissor lifts is that they are all symmetrical. In order to work, the distance from the loaded point to the crosspoint must be the same as the distance from the crosspoint to the ground. This ensures that weight is distributed equally throughout the scissor lift beams.
  
  

Power

• Since scissor lifts have such a wide variety of use, they also have a wide variety of power sources. Scissor lifts for lifting cars can be powered electrically, sometimes from the car's cigarette lighter. On the other end of the spectrum, industrial scissor lifts that people stand on are often powered by diesel, although electrical options do exist.
  
  

Single vs Multiple

• Scissor lifts basically fall into two categories: single scissor lifts and multiple scissor lifts. A single scissor lift has just two crossbeams and one "x." This means it can only go so high because the length of the crossbeams restricts the height of the lift, and making them too long would make it both unstable and unwieldy.
  
  On the other hand, multiple lifts have beams crossing each other, then attaching to more beams that go the opposite direction. This allows the scissor lift to rise higher.