Bloc-O-Lifts offer adjustment with force support, damping, and progressive locking through the entire travel. This is achieved by a special piston valve system. When the valve is open, the Bloc-O-Lift provides force support and damping. When the valve is closed, the gas spring locks and provides very high resistance to any motion. Bloc-O-Lifts can be locked and held in position with either rigid or elastic locking. Bloc-O-Lifts are available in a wide range of travel lengths and forces. Bloc-O-Lifts are maintenance free and provide a long service life, even at higher loads. Applications in the Medical and Industrial areas include backrest and height adjustment for treatment tables and beds, steering column adjustment, and exercise equipment.