Let's take a door at all of the components of the 6 panel, stile-and-rail door.
- Top rail.
- Lock rail.
- Bottom rail.
- Stile. For clarity, the accompanying image indicates only one of the stiles. However, on the right-hand side there is another stile of equal size.
- Mullion. It is interesting to note that windows have a similar vertical component, also called a mullion.
- Panel. Six panels of three different sizes comprise this door.
- Casing or Trim. Casing is not actually part of the door itself, but since I get so many questions about door casing, I thought I should mention it. Casing, also known as trim, is the very outer-most wood perimeter of the door. It is attached to the doorframe, not the door itself.