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