One of the biggest advantages of a well-designed scissor lift is the fact that the weight of the load will always remain over the base of the robot and thus help the robot to remain upright. With lift systems like the four and six bar lifts, the load will be moved up in front of the base which can cause the robot to fall forward. Another advantage of the scissor lift is its collapsible nature. A scissor lift can often compress to almost completely flat which allows for the robot to fit within size restrictions or pass under overhead obstacles, such as those that appeared in the Toss Up competition. One of the issues with scissors lifts is the precise calibration that they demand. Both the left and right sides of the lift must move up and down in almost perfect unison. If the two sides are not aligned properly, the lift may start to bend to one side or another. This could cause a loss of game object due to a non-horizontal containment field or cause the robot to tip over due to a center of gravity that is no longer above the base of the robot. In order to prevent this, the lift must be carefully constructed, constantly inspected, and the code should take advantage of many sensors to ensure that the motors controlling the lift are working at the same speed and power.