Contrary to the common idea that a door is meant to provide an opening to a building, its real purpose is to close up an opening. Like windows, doors are shut to prevent harmful climatic elements from entering the building, although in some cases, doors are opened to allow breeze in and provide natural ventilation. With this, it can also be said that doors also function to control the traffic of air and other materials going in and out of a building. A typical door has a number of fundamental parts making this purpose work.
Gravity is the force that pulls objects toward the center of the Earth. That's a principle taught early in school as you can probably remember. It is gravity that gives everything on this planet a certain weight. Above a typical door is a wall that has weight. It differs from the rest of the walls of a building because there is nothing underneath designed to carry its weight. Chances are it will sag and pull down connecting structural parts. The door’s lintel, placed above the doorstep, carries the load and prevents sagging.
In the movie Prince of Egypt, God told Moses that for the Angel of Death to spare a house from the curse of the death of the firstborn, the Israelites must coat the jambs of their doors with lamb's blood. The jambs are the vertical posts that form the sides of a door frame. Home builders are careful in installing these jambs to allow the door to open or close without leaks.
A builder of doors HawaiiTrustedRealty construction firms, which offers remodeling houses Hawaii recommend designs a door with a doorstop to limit pivot and to prevent the hinges from breaking. This is a thin slat chiselled along the door frame to stop the door through the edge. The doorknob is usually installed tangential to the slat for easy closing and locking.
Like windows that have a plank underneath to seal off the window frame doors Honolulu, HI builders install also have sills. This is a horizontal beam below the door designed to lock up leak points. Sometimes, door sills are also meant for lifting the base of the door to prevent permeation due to flooding.