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Home > Projects & DIY Toolkit > How-To Articles > Making Box Joints

Making Box Joints

Box joints are significantly stronger than regular butt joints. They provide more gluing surface and some frictional hold as well. In addition to being stronger, box joints are much more attractive than butt joints. The contrasting side and end grains create a decorative checkerboard effect and pay homage to the builder's skill and craftsmanship. Lowe's is happy to provide this information as a service to you.

Tools & Materials


  • Table saw or router
  • Dado blade
  • Tape measure
  • Drill/driver with bits
  • Clamps
  • Wooden mallet
  • Goggles
  • Dust mask


  • 2 x 6 lumber
  • Wood stock
  • Screws
  • Wood glue

Make the Jig

SAFETY NOTE: Blade guards have been removed in all photos for clarity.Never operate your power equipment without guards and other safety devices in place.

  1. Cut a straight piece of 2x6 30" to 36" long. The 2x6 is the mitre gauge extension.
  2. Measure from one end, along the mitre gauge extension 13", and make a mark.
  3. Install a dado blade on your table saw and set it to the width you want for the box joint tenons. As a general rule, the tenons are the same width as the thickness of the stock you are joining.
  4. Set the dado blade height. Set the blade 1/32" to 3/32" higher than the stock thickness.
  5. Align the mark on the mitre gauge extension with the centre of the dado blade and cut. The dado you make with this cut holds the key in place.
  6. Align the mitre gauge extension with the blade for a second cut. Set up the second cut so the distance between each dado is exactly the same as the width of the dados. Make the second dado (see "Image A").
  7. Cut a block of wood 6" long and the same height and width as the dados. The block is the key in your jig. Secure the key into the first dado with a countersunk screw (see "Image B"). Don't glue the key in place, or you won't be able to replace it if it becomes worn or broken.
  8. With the saw unplugged, align the second dado with the dado blade and secure the mitre gauge extension to the saw's mitre gauge. You may use any method you wish to secure the mitre gauge extension to the gauge. We simply ran drywall screws through the grooves in the gauge into the back of the extension (see "Image C").
Image A

Image A: Cutting the second dado.

Image B

Image B: Both dados with secured key.

Image C

Image C: Mitre gauge extension in place.

Good idea: While you have your equipment set up, make several box joint jigs in different sizes and store them for future use.

Make the Box Joint

Once the jig is made, the most difficult part is behind you. However, you should practice making joints in scrap before you begin on your project pieces. Always make a test joint each time you reassemble the extension to the miter gauge. Remember, if you aren't testing on scrap you're testing on your project.

  1. Stand the work piece on end, flat against the extension, with one edge butted against the key.
  2. Hold the work piece firmly against the extension and make the first dado in the work piece (see "Image D"). Make a small x on the tenon created by this dado.
  3. Reset the jig and place the dado over the key. Make a second cut. Continue cutting dados until you run out of board (see "Image E").
  4. Cut dados in the second work piece. The second work piece should mate to the first so the dados must be offset from those on the first work piece. Place the first work piece over the key with one full tenon (the one marked with an x from step 2) between the key and the blade. Butt the second work piece against the first one and make the first dado in the second work piece (see "Image F"). 
  5. Remove the first work piece from the jig and continue making dados until you run out of board.
  6. Glue and clamp the pieces together to make the box joint (see "Image G"). If you want, you may use finish nails to strengthen the joint.
  7. Since the dado blade height was set slightly deeper than the width of the stock (Step 4: Make the Jig), you should sand the raised end of the joint flush with the face of the board to which it is joined.
Image D

Image D: First work piece with edge against key.

Image E

Image E: Continue cutting dados.

Image F

Image F: First cut in the second board.

Image G

Image G: Finished joint.

You can also make box joints with a jig on a router table. The jig and set up are the same, just substitute an appropriately sized router bit for the dado blade used in the table saw.

Back To Lowe's For Pros

Tools, products, materials, techniques, building codes and local regulations change; therefore, Lowe's assumes no liability for omissions, errors or the outcome of any project. The reader must always exercise reasonable caution, follow current codes and regulations that may apply, and is urged to consult with a licensed professional if in doubt about any procedures. Please visit our terms of use.

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