Check valves are used in hydraulics to __________.

Check valves are crucial components in hydraulic systems designed to allow fluid to flow in only one direction. This function is essential for preventing backflow, which can lead to system inefficiencies or damage. By blocking flow in the reverse direction, check valves ensure that the intended flow path remains unobstructed and that the hydraulic system operates correctly.

In hydraulic applications, controlling flow is typically achieved through other devices like flow control valves, while speed control is managed through devices such as flow restrictors or variable-speed drives. System pressure is regulated by pressure relief valves or pressure regulators. Therefore, while options like controlling flow, speed, or pressure relate to various aspects of hydraulic systems, the primary purpose of a check valve is to block flow in one direction, thereby enhancing the reliability and efficiency of the hydraulic circuit.