Canadian Woodworking

A square peg into a round hole?

Blog by Rob Brown
Square Tenon

It turns out putting a square peg in a round hole is possible, and it actually worked quite well.

I had to add a faux peg detail to a vanity I made recently. The project involved measuring up an existing vanity and making three more to match. The existing vanity had a faux square peg in the leg, near where the lower rails joined the legs. I wanted to complete this in the simplest way possible, and not take a ton of time to do it.

Start with the round hole

My plan was to drill a hole in the legs, machine a length of the contrasting wood to 1/2″ square, machine a square tenon on one end of the length, ease the tenon a bit, cut the plug to length so the protruding part of its head was about 3/16″ long, pillow the face of the plug and install it.

Since I knew the plugs needed to be 1/2″ square, I thought I’d see if a 7/16″ diameter hole would work best. I drilled a hole in a piece of scrap so I could test the fit of the square tenon in the hole, then snuck up on a tight fit when machining a small rabbet on all four sides of the length of contrasting wood. I wanted it tight so I could ease the four edges with a file and give the glue a bit more surface area to make contact with the inside of the bored hole.

I raised the dado blade in my table saw bit by bit as I approached what I felt was a good depth of cut, then I eased the four edges with a file and tested the fit. After a few more dado blade height adjustments it was perfect.

At this point I made the faux plugs I needed by rabbetting the cheeks, easing the four edges, cutting the plug to length and repeating.

Be careful - belt sanders bite

When I had all the plugs done, including a couple extra ones just in case, I pillowed their ends on my belt sander. A word of warning: A belt sander is generally a fairly aggressive power tool that does a great job at removing lots of material fairly quickly, even with a 120 grit belt, but it’s not easy to sand a small surface and only remove a small amount of material. I rested the belt sander on its edge, used my right hand to operate the trigger and carefully manipulated each plug with my left hand, always ensuring to press very lightly into the sanding belt and to grip the part towards the lead end as much as possible, as that would reduce the chance of the belt sander gripping the part and flinging it across the shop.

A few times the plugs got caught up on the belt and went for a ride. Luckily, my fingers never got hurt by the flying plug and my fingers never came into contact with the moving belt. I’ve removed skin on my fingertips several times, so I’m always careful when sanding freehand with my belt sander.

Glue, then a few gentle taps

A light hand sanding eased the sharp edges and gave me a smoother looking plug to install. I applied glue to the inside of the hole and the square tenon with a small brush, inserted the plug in the hole and seated it with a few light hammer taps.

Only once did I break a corner of a plug. A tiny bit of glue and careful placement of the broken piece hid all signs of a struggle.

Little details like these faux square plugs are what add a bit of character to a piece of furniture and separate a custom-made piece from a store-bought, mass-produced piece. On the other hand, it’s sometimes the lack of extraneous details that could clutter the look of a piece that makes custom-made furniture especially attractive. It’s always a balancing act to know when a piece of furniture needs that extra something to bring it to the next level, and to know when to stop adding details to a piece that might clutter it up. This was easy for me in this situation, not because I’m an expert in knowing when to add details and when to stop, but because I was aiming to replicate an existing vanity that already had this square plug detail.

Some say the key to great design is knowing how to take away all the unnecessary details so you end up with just the essence of the piece. I’d say there’s a lot of truth in this approach.

Square Tenon

I started with machining a square tenon on the end of a piece of cherry.

Square Tenon

Round the Edges

Since surface area is one of the keys to creating a glue joint that’s strong enough for the application, I filed the four edges to give me an advantage. This also allowed me to more easily insert the plug into the hole.

Round the Edges

Cut It Off

Although you could use a machine of some sort, a Japanese hand saw is the perfect tool to make a fine cut like this and trim the plug to length.

Cut It Off

Pillow the Face

I carefully touched each plug on the belt sander to give its face a facet. Repeating this three more times per plug left me with a nice, even plug face.

Pillow the Face

Tap, Tap, Tap

A few gentle hammer taps allowed me to seat the plugs properly. An errant tap, whether it’s too strong or misplaced, could result in breaking the plug. Don’t ask me how I know that.

Tap, Tap, Tap

All Done

The square plugs are now all in their respective round holes. Installation awaits!

All Done
Last modified: June 8, 2023

Rob Brown - [email protected]

Rob is a studio furniture maker and the editor at Canadian Woodworking & Home Improvement. Instagram at @RobBrownTeaches


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  2. Hi George,

    I don’t see why you couldn’t hold the plug with a Vice-Grip or other type of pliers. I find my fingers usually work, especially if you’re a bit on the careful side.

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