Introduction: Turn a Fail Into a Feature

Picture of Turn a Fail Into a Feature

So there I was at then end of the day, fitting the last ash wood window sill I had made for a friend's house, and oh no, it's not big enough!?

Yes I know... Don't give me that measure twice business, it still happens, and when it does what are you going to do?

Having made this particular sill from scratch (and I mean from scratch, having felled  and chainsaw milled the tree myself (more on the DIY chainsaw mill in the future)), I didn't really want to give up on it.

Lets add a bit of length and make an interesting and unique feature of it. Adding length to a board of wood is difficult - even if you find a grain and colour matching piece of wood, end grain gluing doesn't work. In short trying to make an un-noticeable addition is very difficult and will probably look scrappy anyway (and it's a bit boring).

Better we thought to make a feature out of it, make it look like a playful and deliberate addition - something cool to remember the comedy of a too short plank. 

I'll go over the method I used.     

Step 1: General Idea, and Tools Required

So you have seen in the photos what it looks like, the same method could be used to fit in any shape you like, but some are structurally better than others. The shape I used was based on the size of a scrap of teak I had left over from some other projects. Contrasting coloured wood is interesting, and makes it look like deliberate fun rather than a botched job.  

The more complicated and large you make your shape the harder it will be to get it fitting tightly, without a gappy joint. I found this one quite a challenge.

Tools used in this method:

Router (with flush trim cutter bit - the bearing on top type)
Jigsaw, coping saw, and/or bandsaw 
Chisel (sharp)
Safety equipment (goggles, ear defenders, dust mask, dust sniper, etc)


Some wood
Your choice of Wood glue  
2 part epoxy and some saved wood dust (useful if you expect to have some small gaps in you joints - you should expect this!)  


Step 2: Draw Your Shape and Cut It Out

Picture of Draw Your Shape and Cut It Out

First find the wood you are planning to join on, check out the sizes, and then draw the shape you fancy. The shape I drew may seem random, and in many ways it is, but it has a few important features. The two sticking out bits near the top mechanically tie it to the end grain of the recipient piece, in this case the ash sill. And the side grain area (the useful glue-joint area) is increased by bulging out at the bottom right.   

One note of warning: sharp bends and pointy bits do look super cool, but will be very hard to do using this method, as the router bit may not fit. They will increase the 'chisel time' significantly.     

Anyway, draw on your shape, and when you're happy with it, cut it out with a jigsaw or coping saw (jigsaw is much faster if you have it, but can be less accurate if your not practised. Either method has a significant problem: the cut will rarely be completely perpendicular  to the wood. When you cut tight corners and curves the jigsaw blade will tend to bow and deviate from a true up-down vertical path. As we are going to be both jointing to this cut edge and using it as a template to make our insert piece, this is significant.


Step 3: Tidy Up the Cut Edge

Picture of Tidy Up the Cut Edge

Time to get the router out and set it up with a flush cut bit. I'm using a 1/4" shank with a 1/2"bearing and cutter dia. We want the guide bearing on top type. The router bit will replicate whatever the bearing rolls across, so before you start, sand away any unwanted ridges left by the saw blade. A bobbin sander is excellent for this, but we don't have one, so careful hand sanding is in order - a dremel type rotary tool can also come in handy here. You only need to saw the top of the edge where the guide bearing will run - that's the bit that the cutter will replicate. 

When happy run the router round the cut edge to smooth off the cut and ensure that our edges are exactly perpendicular. Depending how straight your saw cut is, you may have to flip the workpiece over and rout from the other side as well. This eliminates the undercuts - whereas the router pass from on top removes the slopes and makes the edge sheer.  

Once you are happy that you have a clean and consistent edge to join to, it's time to use it as a template to make your insert piece.

Step 4: Rout a Small Edge on the Inset Piece

Picture of Rout a Small Edge on the Inset Piece

We need to firmly clamp the inset piece to the bottom of the wood we just cut a shape in. If the insert piece is small there is no room for clamps, because they catch on the router. In this case use three or more strategically placed screws to firmly secure it to the bottom. 

Once it is safe and secure rout a shallow grove in the insert piece that copies the cut edge. See picture comments for details... 


Step 5: Follow the Line & Cut the Insert Piece

Picture of Follow the Line & Cut the Insert Piece

Unscrew the insert piece and mark up what needs to be removed - that's everything that was the other side of the the shallow grove you just routed. 

Ideally use a finely tuned bandsaw (if not a jigsaw or coping saw will do) to cut close to the grove. The more of a bandsaw jedi you are, the closer you can sneak up to the outside grove line (I aim to leave about 0.75mm of material between the saw kerf and the edge of the routed grove). 


Step 6: Sand to Perfection

Picture of Sand to Perfection

Now in an ideal world you use a disk sander and a bobbin sander to carefully sand away the remaining material until its a perfect fit. As it is I don't have either of those things so an upturned belt sander is clamped to the bench... The tight inside curves are impossible to get into with a sander, so use a sharp chisel to tidy up there.  

The little side-wall of the routed grove is a good indicator, when that is sanded off you know it's time to stop. Take your time and stop to check the fit often - it's easy to do too much.     

Step 7: In Place

Picture of In Place

When it is fitting tightly in there (don't force it if it is too tight or bits will brake off), apply wood glue to the edge and tap or use clamp pressure to get it in place. Leave the bottom of the routed grove flush with the original wood (you can plane the raised section of the insert piece before or after it is secured in place - which is easier will depend on how big it is).

Wait for the glue to dry. 


Step 8: Finishing Tweaks

Picture of Finishing Tweaks

If it fit perfectly, that's awesome, skip to the next step and your'e done. If there are a few gaps, then hey, lets fill them to make it look better and make it stronger. I used two part epoxy mixed with some of the teak sawdust to make a runny putty which I syringe into any tiny gaps. Before I do that I create two channels with the hot melt glue gun either side of the joint line. It does a good job of containing the epoxy.

Once set sufficiently all the excess glue (hot melt and epoxy) can be removed with the router, planer or whatever - this is best done when the epoxy is hard but not rock hard, like it goes after a few days - if it is like this it's pretty harsh on your cutting tools. Getting it after about 8 hours seems about right, but it varies with temperature a lot.

Step 9: Sand Flat

Picture of Sand Flat

If you didn't already, plane off the plateau on the insert piece, and sand the whole area completely flush.   
Admire you new weird interesting unique feature.

Thanks for looking through. Would love to hear your comments, question and experiences.

Step 10: The Sills

Picture of The Sills

So here they are all installed. They make some nice window hang out areas.

Thanks for reading, I hope some of you find the technique useful. If you interesting in more of what we are up to check out the Flowering Elbow website


vincent7520 (author)2013-11-11

This guy is a pro !!!…

Puuuuurfect …

mothman92 (author)2013-09-25

quick note on the inlay work.the easiest way i have found so far to make air tight inlays is to put a bit of two way tape in between your blocks and cut away. gives you an exact match and you can get as funky as you want without worry of duplicating it. nice ible :)

GreenMeUpScotty (author)2013-09-25

It looks great and what a conversation piece it is!

SteveDonie (author)2013-09-25

Several years ago I built a china cabinet, and the base I built somehow got mis-measured and turned out too small front-to-back. I ended up sawing it in half and adding some contrasting wood diamond shapes in the cut, with a screwed-in brace along the back to keep it strong. It added a lot to the final project!

Eh Lie Us! (author)2013-09-25

man, this project just floors me.

ejb (author)2013-09-24

Nice - Great looking work

I'm interested to see more about the DIY chainsaw mill!!!

bongodrummer (author)ejb2013-09-25

In the pipeline. Keep an eye on the FE blog...

jsolterbeck (author)2013-09-24

This is the best instructable I've seen in awhile. Highly entertaining captions! I learned a few new techniques, and I'm usually thrilled to learn just one. Can't believe you picked such a crazy shape to replace but I dig it, and especially the grain directions running amok. Why not? Cheers mate -

bongodrummer (author)jsolterbeck2013-09-25

Grain that runs amok - love it :)

Makescreenname (author)2013-09-24

Great instruct. I also thought it was a puddle from a leaking window, but then it occurred to me that's great "psychological woodworking"-- the natural reaction to a puddle by a leaky window is to go look at it, maybe get a paper towel to clean up, but then, on closer examination, you see what it really is---and appreciate the clever deception! Nice job, and thanks for posting.

Haha, cool. Am loving the different reactions it gets.

David Trees (author)2013-09-25

I love natural furniture and design. We used own a 1.5 long N.E coffee table. Sadly we sold it before we moved to the U.K. It was made from Camphor Laurel. So when we came home at night from work there was a beautiful earthy smell of natural camphor in our little 10m x 10m house. ( a converted 3 car garage + workshop).

Where are you based? Where did you source your N.E timber from? Really nice job BongoD :) Congrats!

Thanks for taking the time to post this how to article

bongodrummer (author)David Trees2013-09-25

Hi David. Thanks for the encouragement. The coffee table sounds good. I haven't ever used Camphor Laurel, but apparently (ok my quick wikwikipedia look suggests) it has volatile chemical compounds in all pats of the tree - which would fit with the strong fragrance of the wood. I guess extra precautions when making dust and working it would be in order..
Like the living in a converted garage idea.

Not actually sure what you mean by N.E timber(?) but I'm guessing you mean the teak. It was a scrap we had left over from some other projects, but the wood came to us originally from the local university, who were 'brutalizing', (erm, I mean 'modernizing') their science labs. Teak was often used for science benches because of it's excellent chemical resistance. 

I'm based in West Wales. If your anywhere nearby, Flowering Elbow's having an open workshop day soon, come along!

I say West Wales, but the shop is a little more mid - near Carmarthen.

danielhwolf (author)2013-09-25

Awesome! I love it. Have my own history of fails-into-features, but none as nice as this.

MarkML (author)2013-09-24

Beautiful work! Excellent Instructable, very well written, concise, but provided a wealth of information. As a mere amateur, I learned several techniques that I haven't seen before. Thanks for sharing your excellent ideas!

dalesql (author)2013-09-24

Very cool feature. Great save. +1

Shooglenifty (author)2013-09-24


Go on the Celtic Welsh.

webdeblee (author)2013-09-24

Love this! great example of saving a project, thanks!

Ray from RI (author)2013-09-24

So was the design you used, suppose to represent some kind of animal real or imagined??? Just curious?

bongodrummer (author)Ray from RI2013-09-24

No not really, it was a compromise made between me, the pencil I was using, the size of the hole that needed filling, the grain of the ash and the shape of the teak off-cut I had to work with. In other words, it was kind random... But one of new owners have likened it to a dolphin and the other thinks it's a mole shape.

dwosullivan (author)bongodrummer2013-09-24

I thought it was supposed to look like a damp puddle, like the window was leaking! It makes you look twice :-)
Very nice work. I had never thought about using a trimmer to straighten a jigsaw edge either - but I don't have a lot of experiences with routers.

Ray from RI (author)bongodrummer2013-09-24

Hey what ever works.. it was a good save

LynxSys (author)2013-09-24

Very nice work, the fit is perfect! I used to use the upside-down belt sander trick (from step 6) a lot, so I eventually built a jig to make such tasks easier, and keep things square:

It's helped me reduce my number of belt-sander manicures, too!

Bettybstt (author)2013-09-24

Really nice job! Wish I had thought of this for some of the mistakes I've made. Your attention to detail is delightful. Nice instructable.

nic nak (author)2013-09-24

"he who never made a mistake, never made anything", nice rescue, looks beautiful.

SussoGobbino (author)2013-09-24

Amazingly smooth! And the view from the window is awesome, where is it?

Thanks, it's in West Wales, on the coast. The pictures definitely don't do it the view justice. Our friends run a guest house so you can even stay there :)

Looks great! Unfortunately, I'm too far away and I can't afford to go on a vacation ^^

shannonlove (author)2013-09-24

"Yes I know... Don't give me that measure twice business, it still happens, and when it does what are you going to do?"

Mistakes are always going to happen. If you can do any kind of work without error, you need to get out of the craftsman business and get into the the laying on hands and other miracles.

I believe it was the late, great James Kernov, himself that said that graceful error recover was the true mark of a master craftsman. The goal isn't to be perfect in the shop, the goal is to deliver   a piece that the end user sees as high quality. How you reach that goal is largely irrelevant. 

Even if you could prefect yourself, you can't prefect the natural wood which is always hiding some invisible biological unique that arose when the tree was alive. It is the biological form and variability that give wood its great beauty but it also makes it impossible to predict exactly what you will find as you work it. 

Once, I  found a near completely spherical knot about an inch inside a piece of oak. Must have been the start of a carbuncle or burl that then got encased by healthy wood. When cut into by the table saw, it just popped out leaving a marble sized hemispherical dent in the wood. At the time, I had no idea how to fix that and had to abandon the piece. That was an expensive lesson in humility.

Turning a mar into a decorative accent is a time honored practice. Even better, it make the piece utterly unique, a factor of potential financial and sentimental value. 

Well, done. 

bongodrummer (author)shannonlove2013-09-24

Couldn't agree more. Mostly all what makers do is make is mistakes, the trick is in working out ways to make them happy :)

OutlawKtulu (author)2013-09-24

Nice Save!

I will take away one thing that I will use in my future projects, Hot Glue Gun Channels! I like that!

bongodrummer (author)OutlawKtulu2013-09-24

Yep, hot melt channels are useful . Also, love the way you picked out something to take away - good attitude. You may not like a project, but there's almost always some inspiration in there somewhere ;)

rednemo (author)2013-09-24

Many carpenters I've know don't even measure once -- they just eyeball it. The trim will cover any gaps!

bongodrummer (author)rednemo2013-09-24

Ba professionals... Quick and dirty wins the day.

timmyzog (author)2013-09-24

Beautiful fit and finish. I noticed that you changed the direction of the wood grain on the patch. When designing in wood, it is important to think about what happens as wood expands and contracts. Windowsills end up getting a lot of sun and moisture so the changes can start to cause failures at seams. I think this piece is small enough so that it won't break. Let us know how it goes. I really like it!!

bongodrummer (author)timmyzog2013-09-24

Hay Timmyzog. About the grain direction: very true! During dry periods it will not shrink as much along the length of the grain - I will add that important consideration to the 'able when I find the time. The piece I added was at a diagonal, so not as bad as if it was completely perpendicular. The direction of the grain was kinda dictated by the size and shape of the off-cut of teak I had to work with. Like you, I think it was small enough to be ok though. Certainly a big consideration for large patches though.

djkraz (author)2013-09-24

Thanks for the great instructable! I'm a huge fan of mixing contrasting woods on my furniture so it's great to see some good instruction on how to get creative with it. I must say though, the shape you went with is not very pleasing imho...sorry. Very nice work though!

tioshrek (author)2013-09-24

damn!!! great job! a horrible feeling when that happens but it's even better come up with a nice solution for a problem!

thanks for the share!

gantzeka (author)2013-09-24

What creative and beautiful sills. I love the irregularity. The 'goof' turned 'unplanned success' really fits. I love these! Great job.

audreyobscura (author)2013-09-23

Amazing technique! Thanks for the share.

Thanks for the nice comment!

kenbob (author)2013-09-23

Not that I would ever cut too short....... but thinking I could use this sometime...:) Great instructable.

bongodrummer (author)kenbob2013-09-23

I'm sure you would never make such a schoolboy error ;)

digitalbeardan (author)2013-09-23

Ha Ha !! Not only is the 'stucti' cool, I believe everyone can take a lesson from your, "don't freak out," attitude! Well done!

Thanks for the positive comments. It was more complicated because it was for someone else - luckily they are really into creative and exciting stuff and liked the unusual feature.

redchamelon (author)2013-09-23

Love the view from your window ;)

bongodrummer (author)redchamelon2013-09-23

The view from those windows is nice, but it isn't our house, it's our friends. It was hard to fit the windowsills and not just stare out...

About This Instructable




Bio: BongoDrummer is co-founder and member of Flowering Elbow. He loves to learn about, invent, and make things, particularly from waste materials. Check out his youtube ... More »
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