The article deals with a design of the adjustable lightweight safety device made from composite materials and used for reversible plows. Initially, a design scheme was developed. It was theoretically and experimentally investigated. Research was conducted by the Department of Tractors and Agricultural Machines of the Gorsky State Agrarian University. As a result, software was developed. It is used to determine rational values of the main parameters of the safety lock. The following values of the parameters were obtained: the diameter of fiberglass rods dr = 16 mm; the rod length lr = 0.85 m; the number of rods nr = 16 (8 in each spring); the height of the center of the stop e = 0.15 m; the radius of the crank rr = 0.12 m; the rod length lr = 0.25 m; the initial value of the angle of crank rotation acro = 30 … 700. During the laboratory experimental studies, using the strain gauging method, we studied a change in the traction resistance of a section when it is deepened, and reliability of obstacles of various heights. The traction resistance was 7800 … 11600N, which is sufficient to ensure reliable operation of the plow section in the North Caucasus region. In all experiments, a decrease in the traction resistance was observed when the section returned after deepening to its original position, which was caused by the gravity section and hysteresis losses in the composite rods. Field tests of the upgraded model of the reversible plow PON-3 confirmed high efficiency of the safety lock design.