Attaching sofa legs and assembling furniture is made much easier by the ability to insert metal thread pockets into wooden surfaces. If you have never done this project it may be a mystery to you; like most other things in wood working and home repair, once you know what tools products and tricks to use the mystery unravels itself. This particular mystery is solved with a little piece of hardware known as a T nut. Take your furniture leg, or other hardware you need threaded, to the hardware store and use their thread templates to determine the size and thread gauge you will need to complete your project.
Mark the spot where the item needs to thread into the wood surface using a tape measure and square for precise placement.
Consult the installation instructions that came with your hardware for precise sizing details. Use the recommended size for best results. If you have no instructions, compare your T nut hardware to your drill bits until you find one the same size as the outside dimension of the thread pocket of the T nut. Hold the T nut up to the bit and wrap a piece of masking tape around the bit, just a little further back from the tip of the bit, than the T nut is long.
Drill a hole in the marked location using the bit you sized in the last step. Drill the hole to the depth marked by the tape. Keep the drill as level as possible so that the threads will go straight in. Blow the dust from the hole. Apply construction adhesive to the back of the face of the T nut.
Fit the T nut into the opening of the hole and tap it firmly in with a hammer until the ring at the top of the sleeve is flush against the face of the wood. Thread the Allen bolt into the T nut. Insert the Allen wrench into the bolt head and twist firmly until the T bolt shifts slightly, locking the twisting barbs on its sides into the wood.
Twist the bolt out of the T nut and check to be see that it did not come loose. If it came loose, repeat installing the bolt, twisting with a little more force until the barbs set and the hardware can be twisted back out without disturbing the t nut.
Allow the adhesive to set for one hour. Install the leg or other hardware into your t nut.