Everything You Need to Know About Parts of a Door

September 24, 2020

Have you ever counted how many doors are in your home? There are many more than meets the eye, from the laundry room door to every single closet room door. These hinged, sliding, frameless, and sometimes revolving barriers are an access point to greeting friends and guests, while also keeping other people and elements out. Whether installing a door replacement or fixing broken parts, doors are a complicated component of the home as you’ll see in our door parts terminology series below. 

Common Door Terminology 

Parts of a door

Astragal- Running from the door sill to the door head, this piece runs vertically between double doors. 

Bottom Rail- This bottom rail serves the same purpose as the stiles and top rail, to frame the door panel along the bottom. 

Casing or Frame- Also referred to as the door sash, this includes the entire framework that supports the door panel and consists of the sill, jamb and head. 

Door Sweep- This is the seal between the sill and door frame that contains weatherstripping, and ultimately increases the energy efficiency of a home. 

Door Stop or Rebutted Jambs- Door stops are wooden pieces fitted into the doorframe to prevent the door panel from swinging beyond its closed point and damaging its hinges. 

Fixed panel- The fixed panel is the panel of double doors that locks into place and does not open or close with the other moving panel. 

Hinge- A door hinge is the joint attached to both the door frame and panel that pivots the door panel when opened. 

Jamb- Head Jamb is the upper piece of the door frame that runs horizontally, while the Side Jambs run vertically on the hinging and strike plate sides of the door frame.

Latch- A door latch is the part of the door that holds the door shut. By turning the doorknob, the mechanism will pull the latch into the door panel allowing it to be opened.

Lock Rail- Not every door has one, but a lock rail is the intermediate horizontal board that holds the lockset into place.   

Mullions- If a door is divided into four panels, mullions (mull) acts as a seam running vertically down the center of the door, intersecting the lock rail. 

Panel- A panel is the door itself that swings open and closed. 

Sill- Also referred to as a threshold, a sill is the part of the door frame that sits on the floor underneath the actual door. 

Stiles- Stiles, including both the hinge and lock stiles, are the frames of a door panel on either side.

Strike Plate- This is a metal plate that protects the latch from damaging the door jamb when the door is closed.

Top Rail- This top rail serves the same purpose as the stiles, to frame the door panel on the top. 

Related Door Terminology

In-Swing or Out-Swing- These refer to the direction which the door panel swings when opened, into or out of the door.

Threshold- Also referred to as a sill, a threshold is the decorative element that transitions the door sill to the actual landing floor of the room, creating one seamless entryway. 

Transom- A transom is the horizontal beam separating the door frame from a potential window above. 

Opening- An opening is the gap in the wall that fits the door frame, fitted with wooden wedges called shims.

External Door Terminology

Door Knob- This is a customized piece of hardware that is screwed into a door panel. By twisting the door knob, the door will open.

Door Trim- Door trims are another decorative element creating the finished product that hides the door frame, shims, and jambs from being visible. 

Glazing- Glazing is the glass inserts in the door panel. The thickness varies depending on the glaze. 

Hangers- Hangers are the hardware along the top of door panels holding sliding doors into place. 

Key Lock or Lockset- Enables a door to be locked shut or unlocked using a release mechanism, sometimes a key. 

Rails or Tracks- In the event of sliding doors, rails and tracks are the runners that door panels will slide along. 

Rollers- Attached to door hangers, rollers allow the panels to slide effortlessly along the rails.

Sidelight- Sidelights are glass panels on either or both sides outside of the door frame that allow sunlight into the home.

Parts of a Door Determine Door Styles

As shown in the diverse terminologies above, not all types of doors share the same anatomy. Depending on the number of door panels, styles of door frames, and hinge requirements, your door could be one in a million. 

Framed vs Unframed

These are your typical entryway and interior doors. Framed doors contain frames around the panels for support. The panels may consist of ornate glass inserts to allow sophistication and character. Frameless doors do not require door frames and are suspended in the opening with hinges and metal accent lining. Both provide the structure and functionality needed, but offer two very different styles.


Another aesthetic-inspired functionality of the door is a sliding one. Rather than a door panel pivoting on a hinge, it is mounted onto hangers and rolled on tracks to slide opened and closed. An example of this in a space would be artistic sliding barn doors

Why Should You Know Common Door Industry Terms?

Doors are the gateway to many aspects of our lives. They enhance curb appeal, maintain privacy, and create an energy efficient home. Understanding the various parts of a door allows a necessary foundation to be able to effortlessly replace one and maintain these functions. If you are in the business to replace a household or office door, shop our endless door options and contact us with further questions.