Mechanical Engineering

How Horizontal Blinds Work

The mechanics behind a window blinds

By: Megan Lai, Journalist

March 18, 2025

Every time you walk into a classroom, it’s likely that you see window blinds. But how do they work? What are the components and the mechanisms hidden in the blinds that make them retract and turn? Read on to find out more.

Components of the Pulley System

There are many components that work together to operate a window blind. First the wooden looking boards that go across the window is the slat. The slats are usually made up of materials like wood, plastic, vinyl, or others. The slats are held in place with string that rest below, around, and through them. There are holes in the slats for the string to go through it to help with adjusting the blinds. The set of two strings dangling on one side of blinds can be pulled to retract the blinds, making them rise up while stacking on each other. On the top of the blinds, the board covering the headrail (box looking container holding the turning mechanism) is called the valance, and the valance clips hold the valance onto the top of the blinds. On the bottom of the headrail, there is a a small hole in which the two pulley strings come out of. One of the lift strings (name of the string) is connected to one side of the blind, and the other lift string is connected to the other side of the slats. If you pull both together, the headrail will act as a pulley, pulling the blinds up. However, if you tilt the pulley strings to the toward the side the the strings are on (in terms of the blind), the blinds will lock itself at the point where you stopped pulling. How does this work? Above the hole in which the pulley strings come out of, there is a metal piece called the chord lock. This piece is what makes the string be able to be pulled easily, since the strings rest on a wheel. However, on the other side of the the chord lock, there is a textured cylinder tube that can move up and down, when you are pulling the string to the side, it allows the textured tube to move up, and lock the string with the texture, keeping it in place. Watching the video above will make you understand more with the diagrams.

Components of the Tilt System

On the other side of the blinds, there is a long, cylinder like stick, called the wand. Turning the wand will manipulate the angle of the blinds. How does this work? The wand is attached to a screw that turns when the wand turns. As a reaction, the gear that is connected to the screw also turns. There is a metal rod that sticks through the gear, which is parallel to the headrail box. This turns all of the blinds at once, since the rod is connected to the strings. Therefore, when the wand turns, the blinds tilt up and down.

All of the components of the pulley and the tilt system help the blinds adjust in many different ways. These great innovations can help us block out the sun in our everyday life.