If your vehicle is showing door sags and requires extra force to lift and close, here are the most likely causes and the parts you'll need to fix each one.
The metal pins and soft bushings inside the door hinges wear down over time due to the weight of the door. This allows the door to droop and misalign with the latch, requiring you to physically lift it into place to close.
The bolts securing the door hinges to the vehicle body or the door shell can vibrate loose over time or fail to be tightened properly after bodywork. This causes the entire door assembly to sag out of alignment.
If the striker plate on the door jamb comes loose or is adjusted incorrectly, the door latch will hit it at the wrong angle. This makes it feel like the door has sagged and requires extra force or lifting to close properly.
If the door was caught by a strong gust of wind or had excessive weight placed on it while open, the hinge itself can bend. This permanently alters the door's alignment and causes it to sag.
The door check prevents the door from opening too far. If it bends or binds internally, it can severely restrict door movement and make closing very difficult, sometimes forcing the door downward and mimicking a sag.