The Flying Trolley Glitch allows your trolley to fly and bypass barriers such as the laser doors. To perform the glitch, you must put an object on your trolley (a section of iron fence probably works best for stability, but a box or crate will do in a pinch), jump on the object, and lift up your trolley with the Wrench, while you are standing on the object. Although you can use it to fly, it is a bit hard to control.
Video provided by Bertin428's Youtube Channel