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29 Window Terms You Might Not Know

29 Window Terms You Might Not Know

Old windows are pretty simple, right? I mean, it’s only one little piece of an old house. I’ve often described them as consisting of only wood, glass, and putty and while that’s true, there is a plethora of pieces that make up each window, and knowing these terms might come in handy when working on your old windows, or if you’re a trivia buff.

See how many of these terms you know and up your window smarts by studying the one’s you don’t know. Also, if you’re planning to restore your historic windows this year, be sure to pick up a copy of my book Old Windows In-Depth. It covers everything you’ll need to restore your windows be they wood or steel.

Window Terms

1. Relish – A woodworking term that refers to the reveal left from the haunched tenon design of the sash construction. Some people mistakenly think this is a weep hole, but it is indeed a relish (not to be confused with a sauerkraut).

2. Haunch – The partner in crime with the relish, a haunch is a tenon that has a portion of the tenon removed so as to remain invisible in the final assembly of the sash joinery.

3. Horn or Lug – Sometimes the bottom of the top sash or less frequently the top of the bottom sash has a decorative ogee style swoop that extends beyond the meeting rail. This piece,  while decorative, allows for a stronger joint on the meeting rail to support heavier glass and provide more stability.

4. Ogee – An ogee is one of the most common profiles found on the interior of wood sash. It is a simple swoop with a slight relief on either side of it.

5. Ovolo – Another popular, but less common sticking profile on sash interior profiles is the ovolo. It is more of a quarter round look than the ogee swoop.

6. Mortise – The king of joinery- a mortise is a square hole drilled into a piece of wood that allows it to accept a tenon which will be used to join the two pieces of wood together. There are different types of mortises used on window sash, like a through mortise where the hole goes all the way through the wood and a blind mortise where the mortise is hidden.

7. Tenon – The mortise’s better half- the tenon is a piece of wood at the end of a wood member (usually rectangular in shape and one-third the thickness of the wood) formed to fit perfectly in the mortise and create the strongest of woodworking joints available for long lasting performance.

8. Check or Meeting Rail – The top rail of the bottom sash and bottom rail of the top sash are both called a check rail (or meeting rail, depending on where you’re from). The check rail is designed with either a bevel or a small step on it that mates with the other check rail to create an excellent air seal when closed.

9. Bar – A bar, often confused with a muntin, is a small piece of wood dividing individual panes of glass within a sash. The defining characteristic of a bar versus a muntin, is that the bar runs all the way from one rail or stile to the other, whereas the muntin is interrupted by the bar.

10. Muntin – A small piece of wood that divides pieces of glass within a sash that runs between bars and is either coped or nailed in place.

11. Sill – A sloped piece of wood that the bottom sash rests upon when closed. Often integrated into the jamb with a rabbet and nails through the side.

12. Subsill – A piece of wood installed under the sill proper above. These vary in design but the defining characteristic is that it is a separate piece of wood and under the sill.

13. Apron – A piece of 1×4 or 1×6 (sometimes decorative) installed flat against the wall and just below the stool (see below) on the interior of the window. It is technically part of the interior casings.

14. Top Rail – The horizontal rail on the top of the top sash in a double-hung window.

15. Bottom Rail – The horizontal rail on the bottom of the bottom sash on a double-hung window. It is usually about 1-1 1/2″ taller than the other rails and stiles of the sash.

16. Stile – A vertical member of the sash. (Rails run horizontally) The bottom sash and top sash both have two stiles, one on the left and one on the right that are joined to the rails by way of mortise and tenon joinery.

17. Jib Head Window – This unique kind of window is designed with a pocket above the window into which the sash can be raised into so that it disappears into wall when in the open position allowing for a much larger opening. Often this windows will have sills down near the floor so as to function as a door when fully opened.

18. Blind Stop – A piece of wood usually 3/4″ thick integrated into the construction of the jamb in most occasions that serves as the exterior guide rail for the top sash. It also serves to create a rabbet around the perimeter of the window that a storm window or screen can be installed against.

19. Eastern Casing – Most common in New England homes this form of exterior window casing is installed on jambs without a blind stop and the casing serves as the window’s blind stop.

20. Western Casing – The vast majority of exterior casing on windows outside New England where a blind stop is present and the exterior casing is not integral to the operation of the top sash.

21. Parting Bead/Parting Stop – A small piece of wood, usually 1/2″x3/4″ in size that is press fit (sometimes nailed) into a channel in the middle of the jamb that separates the top sash from the bottom sash enabling smooth operation of both sash.

22. Interior Stop/Window Bead – A piece of trim whose style is largely variable depending on regional differences that is installed vertically along the inside of the bottom sash by nailing, or occasionally screwed-in in higher end applications. This stop guides the bottom sash along its path of travel much like the blind stop guides the top sash.

23. Head Casing – Sometimes plain and sometimes ornate, the head casing is the horizontal piece of trim installed on both the exterior and interior of the window jamb.

24. Jack Sash – A window sash designed without a meeting rail. This sash is most common on single-hung windows since the meeting rail is unnecessary when the top sash is inoperable.

25. Box Jamb – A jamb commonly installed in masonry homes where the weight pocket is fully enclosed by wood framing around it. Box jambs were typically installed before the mason laid his brick and thus served to keep mortar from getting into the weight pocket and affecting the operation of the window mechanics.

26. Parting Slip – A thin piece of wood or metal installed into the weight pocket to keep the sash weights from clanging together or becoming tangled.

27. Stool – Commonly mislabeled as the sill, the stool is the piece of wood that sits directly above the sill and ensures a good seal when closed for the bottom sash. This is what you rest your elbows on when you gaze longingly out the window.

28. Cames – The lead or zinc dividers that hold the many decorative pieces of glass together in a stained glass or leaded glass window or door.

29. Sash Weights – Lead or iron counter balance weights hidden within the weight pocket to balance the sash on a double-hung window.

There you have it! 29 terms you may or may not have known. What else am I missing? What needs to make the list that didn’t?

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7 thoughts on “29 Window Terms You Might Not Know

  1. Great info! RE eastern/western casing, I’ve noticed that the few wood storm windows here in Vermont are mounted on the casing rather than inset in the window so it was interested to read this is pretty much a regional (New England) phenomena. Any idea how this came about? I.e., why New England has eastern style windows while pretty much everyone else has western?

  2. “This is what you rest your elbows on when you gaze longingly out the window.” Great description! 😀

  3. Absolutely fantastic. So helpful.
    I’ve been addicted to refurbishing my 1920s sash windows.
    Recently had to cut a new stile and bottom rail, just wondering if the shoulders of the tenon need to be offset in order to accommodate cutting the relief away from one shoulder to wrap around the stile profile? . No where have I read this but it seems to be necessary as my rabbet and profile match perfectly only there’s a 1/4 inch gap before they meet, just can’t get my head around this, ha ha.

  4. Diagrams or photos illustrating the 29 terms would be very helpful in understanding the location and function of some of the terms.

  5. Some older sash windows have extended tenons that fit into the internal brickwork. What are these extended tenons called? I always knew them as horns.

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