Why is it always that the stile is the mortise and the tenon is the rail?

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Forum topic by zdwiel posted 538 days ago 693 views 0 times favorited 13 replies Add to Favorites Watch
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4 posts in 561 days

538 days ago

Topic tags/keywords: mortise tenon stile rail windows doors joinery

I’ve looked at many doors and windows the past few weeks and every single time, the vertical stile is the mortise and the horizontal tenon is the rail in the mortise and tenon joint in the corners. Is this purely stylistic or is there a functional purpose to this arrangement?

13 replies so far

View HorizontalMike's profile


6923 posts in 1538 days

#1 posted 538 days ago

Good question. I have NO clue though. I suppose it has something to do with standardization of practices/procedures, in order to eliminate any confusion.

-- HorizontalMike -- "Woodpeckers understand..."

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7386 posts in 2272 days

#2 posted 538 days ago

I think it’s traditional. It makes the door most stable in
its longest dimension. If you look at old board and batten
doors you’ll see that they move in width only, and I
reckon that as frame and panel doors evolved it became
traditional to do it that way.

Also, with an entry door with a 6” stile capped by
a rail, the joint is going to move a bit like a breadboard


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404 - Not Found

2544 posts in 1593 days

#3 posted 538 days ago

I would imagine water run off comes into it as well

View teejk's profile


1208 posts in 1308 days

#4 posted 538 days ago

End grain gets hidden that way. Few applications do you ever look at the top or bottom of a door. Plus stability.

View zdwiel's profile


4 posts in 561 days

#5 posted 538 days ago

That all makes some sense. My first inclination was actually that you’d want it the other way around so that if there was water on your sill or threshold you would get minimal end-grain exposure, but that doesn’t seem to be important since the traditional method exposes more end grain on the top and bottom edges.

I like the idea that in both doors and windows you are more likely to be looking at the stile edge than the rails and it might look nicer to not see the joint.


View kdc68's profile


1956 posts in 900 days

#6 posted 538 days ago

I believe too, it have to do with physics (gravity). The shoulder of lets say a blind mortise and tenon joint provides rigidity of downward forces that may be applied to a door or window. If the the tenon was at the end of the rail, then any downward force applied to the stile would fail the joint….Sorry for the crude drawing

-- Measure "at least" twice and cut once

View REO's profile


591 posts in 698 days

#7 posted 538 days ago

had to rethink this a little. on doors of equal sized frame members there would really to no advantage but on those with larger dimensions for the tops or bottoms there would be quite an increase in strength when the tennon has a longer surface on the endgrain. it does eliminate endgrain exposure also.

View TCCcabinetmaker's profile


925 posts in 979 days

#8 posted 538 days ago

1 it allows for wood movement.
2. it increases the stength of the joint for the tenon to not run against the grain of the wood.

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

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1956 posts in 900 days

#9 posted 538 days ago

I reread my post and I thought it didn’t make much sense. I knew what I meant :-) So I thought I’d try again. As you can tell I’m not at all gifted in SketchUp….so sorry again for the crude drawings

-- Measure "at least" twice and cut once

View BenI's profile


326 posts in 802 days

#10 posted 538 days ago

I think if the end grain had a mortise it would make it very weak and easy to split/break.

Also, if the stile had a tenon then the starting width of the board (for the stile) would have to be the width including the tenon.

-- Ben from IL

View bondogaposis's profile


2476 posts in 975 days

#11 posted 538 days ago

It is because of gravity. Glue sometimes fails and and weight of the door would tend to cause the bottom rail to slip off of the tenon if the rail was mortised. kdc68 has it right.

-- Bondo Gaposis

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1956 posts in 900 days

#12 posted 538 days ago

bondogaposis....thanks for that ! I really need to work on my SketchUp skills !

-- Measure "at least" twice and cut once

View rockindavan's profile


283 posts in 1260 days

#13 posted 538 days ago

It also makes putting on hinges easier and stronger. Otherwise hinges might fall between the long and end grain and the screws wouldn’t hold as well.

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