Compressing a standard non-locking Stabilus LIFT-O-MAT gas spring by hand can be extremely difficult because they are pre-filled with high-pressure nitrogen gas designed to support heavy weights. To safely compress one for installation, it is best to mount one end of the strut securely to its anchor point on your vehicle or equipment, and then use the mechanical leverage of the heavy hatch, lid, or hood itself to push the piston rod inward.