• Regardless of their specific design, most windows have certain features in common.Jupiterimages/Brand X Pictures/Getty Images
  
  Among the many styles of windows, certain parts remain the same regardless of the specific design. Of these principal window parts, some are designed for the window's opening and closing while others relate to the window's installation within a wall. When preparing to mount a window, familiarize yourself with those window parts related to its installation. They may function to physically support the window or to protect it over its lifetime.
  
  

Frame

• The window's frame may refer, collectively, to the entire structure that circumscribes its glass portion. Alternately, it may refer to a specific lip-like structure that aids in the window installation, attaching it to the surrounding wall. The metal window frame usually has a flange-like strip extending around its edges. In a metal window, this flange-like window frame typically features prepunched holes, which provide for an easy installation using nails or screws. Once the window is attached via its frame, you may add additional elements, such as insulative caulking or nonexpanding spray foam and any decorative trim molding.
  
  

Apron

• A window's apron is the strip of material that lines it along the bottom edge. It's found beneath the window's stool, a kind of interior sill, and sits flat against the wall. The apron gives the window a finished look. When installing a window, you affix the apron at the end of the project as it is a nonstructural element used to cover up the exposed seam between the bottom of the window stool and the interior wall. In homes where a chair rail crosses the room at the same height as the apron, you might forego a separate apron and simply line up the chair rail to abut the bottom of the window's stool, which will minimize the number of individual trim pieces, giving the room a cleaner look.
  
  

Flashing

• A window's flashing constitutes an important element for its installation though it may come in many forms. Flashing refers to any kind of material used for sealing and insulating around a window or other opening in a building's walls. Ideally, you should use flashing around both the window's head and sill. Acceptable flashing materials include metal, plastic or a self-sticking elastomeric membrane. While you can also find tapes intended for waterproofing, they are typically less effective than the other materials over time. Whatever type of flashing you opt to use, it should carry any water away from the wall and the window structure itself.