Screws increase force by converting rotational force into linear force. When you turn a screw, the thread’s inclined plane increases the distance over which the applied force is distributed. This reduces the amount of force required to overcome the resistance of the object being fastened. The thread’s angle determines the amount of force amplification. Steeper angles provide greater leverage and higher force multiplication. This principle is crucial in fastening applications, where screws provide a secure connection by applying the increased force over a small contact area.