Slatted window blinds block out sunlight as well as provide privacy to home interiors. They raise and lower via a side cord that locks into place inside the upper header rail. If the lock malfunctions, the cord and blinds will become stuck in the raised position. This occurs for a variety of reasons, but you can typically lower the blinds using a manual method.
Grasp the side cord on the blinds and raise it upward until it is level with the top rail on the blinds. Move the cord to the left or the right, which sometimes unlocks the mechanism and allows the blinds to lower.
Place a stepladder next to the window, if needed, and remove the two caps at the left and right front sides of the brackets that hold the header rail in place. These typically slide out toward the center of the window. In some cases, you may need to remove screws to detach this front section.
Grasp the header rail in both hands and pull it out away from the widow. Lay the blinds on a table or other surface where you have plenty of space and light.
Look into the hole where the cord emerges and you will see either a small lever or a small, round cylinder.
Hold the cord to the far right side of the blinds so that it is out of the way. Insert the tip of a flat head screwdriver into the hole and press it up against the lever or cylinder to unlock it. The blinds and cord will lower as soon as you do this.
Raise and lower the blinds three or four times to ensure that the lock mechanism is not permanently broken and then reinstall the blinds back in the window.