I have built a 7' x 13' pergola over my deck and have a slight wobble, so I intend to install some knee braces. Each post has two pairs of perpendicular beams stretching to the adjacent posts. For the brace-beam connection, a simple through bolt will be easy to do. But what's the best way to secure the brace-post connection ?

I was hoping to use a through bolt here too, but can't figure out how to create a surface to hold a washer to the angled face of the brace. Any suggestions?brace-post connection with desired through bolt

4 Answers 4


Prior to drilling the "through-hole", mark the location on both sides and use a paddle-style wood boring bit slightly larger than the O.D. of your flat washer, to make a large flat-bottomed hole.

Make the holes no deeper than necessary to make the nut, washer, and bolt end sit flush (you would need a shorter bolt).

For more precise creation of a flat-bottomed hole you could also use a Forstner style drill bit, but they are significantly more expensive than a paddle-bit. It depends on how nice and clean you want the hole to be.

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  • 2
    I've never heard something referred to as a "paddle bit" where I'm from they were always called spade bits. Neat synonym. Commented Sep 23, 2016 at 17:50
  • My first attempt actually was with a paddle bit. But I found that when only one edge hot the wood, the bit skipped out of place. Maybe that's just me not being very good at handling it. There are several good suggestions in the thread, thanks everyone! Commented Sep 24, 2016 at 15:54
  • It's difficult with a paddle-bit on an angle, follow the advice of @bib answer steps 2-4. Drilling slowly (light pressure) but at high speed works for me. Commented Sep 24, 2016 at 18:21

And another option would be to use a beveled washer. I would use a dado for all of the joints in all of the answers just to avoid slippage strain on the bolt/wood interface. enter image description here

  • Nitpciking: You refer to this as a tenon but based on the picture it looks like a large dado to me. This is a pretty nice option but I think the through-bolt is overkill. All you need the fasteners to do here is keep the wood together. They wouldn't be providing any support.
    – JimmyJames
    Commented Sep 23, 2016 at 18:30
  • +1 to making a lip for the brace to sit on. One or two lag bolts (screws, really) would secure it well. Just be sure to predrill, including clearnance holes through the brace.
    – User95050
    Commented Sep 23, 2016 at 23:59
  • Plus one; either use an ugly tie plate or do this. Fastener type is up to you.
    – Mazura
    Commented Sep 24, 2016 at 0:51

The simplest way is to recess the washer and nut into the angled brace.

  1. Using a spade bit slightly larger than the washer
  2. Mark where you want the hole.
  3. Start a hole in the right side face of the brace, perpendicular to the face of the wood.
  4. As soon as the tip of the bit has a good bite, angle the drill until it is perpendicular to the opposite angle cut of the brace (the left face). Do this slowly and carefully, since only one edge of the drill will be making contact with the wood.
  5. Drill only deep enough to bury the bottom edge of the bit in the wood.
  6. The bottom of this hole will now be parallel to the opposite (left) face of the brace.
  7. Change bit to one just larger than the body of the bolt.
  8. Continue to drill through the brace and then through the upright post.
  • +1. I must have been typing my answer below as you were doing the same, mine is basically a duplicate of yours. had I seen yours first I would not have submitted. Commented Sep 23, 2016 at 16:11
  • @JimmyFix-it Ditto. But yours has great illustrations!
    – bib
    Commented Sep 23, 2016 at 16:50

Minor variation to recessed holes, if you don't have or don't want to buy a spade or Forstner bit: cut a flat face into the angled support. Ensure that you leave at least 50% of the width of the angled support for strength. enter image description here

  • 1
    Or use a chisel to cut only part of the wood out instead of notching the whole piece.
    – JimmyJames
    Commented Sep 23, 2016 at 18:31

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