Some door parts that typically need replacement over time include the knob, the locking mechanism, threshold and the casing, depending on door style and usage. Some doors may also contains windows or pet entries that call for new components and repairs, while others may require hinge replacements as well.
Knobs and locks are among the most common door aspects that need replacing as they are the parts that experience the most use. Many interior doors feature a basic cylinder system wherein the knob controls one spring-loaded latch for keeping the door shut, though the springs or cylinders may weaken over time and start to stick. Some door knobs also loosen, requiring additional turning to pull the latch in and allow the door to open, with repairs ranging from tightening a locking screw to replacing the knob completely. If the knob has a built-in lock that fails to turn or stay in place, it may also call for a full knob replacement.
Deadbolts are another common door component that needs replacement over time, either from malfunction or because the owner needs to maintain security. Door thresholds, which are the components the cover the frame and connecting floor, may also wear and need replacement. Doors with pet entryways may also need new flaps or coverings, depending on usage and style. The seal around some doors also tears with excessive use, calling for a complete resealing.