This is the "muscle." You can use a worm gear for a manual hand-crank system, which provides excellent precision and prevents the lift from collapsing under its own weight. For more advanced builders, a linear actuator or a small motor can automate the process. The Educational Value
: Use a Technic worm gear and a rack gear to push the sliding end. lego scissor lift instructions
This same principle is used in forklifts, aerial work platforms, and adjustable tables. By building this LEGO model, you’ve created a functional, self-locking lifting device. This is the "muscle
You need a stable platform to house the lifting mechanism. aerial work platforms