Summarize this article in one sentence.
T-nuts are circular connectors that attach to the table’s underside. Each T-nut has a central opening used to secure a table leg. When selecting T-nuts, be sure to compare them to the hanger bolts you plan on using. Get bolts that are the same diameter as the opening on the T-nuts.  The equipment you need is available online or at most home improvement stores. T-nuts are useful for tables you plan on moving a lot. They work well on any type of wood table without an apron but are best for unfinished tables. If you plan on covering the table with another piece of wood or upholstery, T-nuts are a good choice. If you are unable to find T-nuts, you can also use threaded inserts. Threaded inserts are similar, circular fasteners that install the same way. Flip the table over to figure out where you will secure the T-nuts. The most important part is keeping the T-nuts equidistant, or an identical distance, from the table’s edges. The exact positioning depends on where you want the legs to be. They are often placed close to the corners but can be moved according to your preference. If you need more precision when placing the T-nuts, measure out from the edges and mark where each one needs to go. Create the holes in the spots where you plan on placing the legs. Keep the holes roughly the same size as the openings in the T-nuts. The exact size will depend on the T-nuts you plan on using, so refer to their length and diameter. It will be labeled on the packaging.  For example, 5⁄16 in (0.79 cm) is a common T-nut diameter. Create same-sized holes with a power drill. Be wary of the table’s thickness so you don’t drill all the way through it. Use shorter T-nuts if your table is too thin to support the ones you purchased. Place a T-nut into each of the holes you drilled. Position them so the wider, circular end is face up. Gradually tap each T-nut down with a light amount of force until it is level with the wood. The opposite end of each T-nut is a central circle with a smaller opening. This side goes into the wood. The base of each T-nut has small blades that will also pass into the wood as you hammer. Arrange the legs so the top part, meant to connect to the table, faces you. Before drilling pilot holes, refer to the diameter of the hanger screws you purchased. Choose a drill size slightly smaller than that. When you’re ready, drill holes that are the same length as the hanger screws.  For accuracy, take time to measure out and mark the center point on each leg if you need to. To make the pilot holes the correct depth, wrap a piece of tape around the drill bit. Position it so its distance from the tip is the same as the length of the bolts. Drill down into the wood until the tape touches it. If you purchased table legs with pre-installed hanger bolts, skip this part. Instead, attach the legs to the T-nuts. Fit a bolt into each leg. Turn the bolts by hand to start the installation and, once they stay in place, finish with locking pliers or an open-ended wrench. Make sure the legs feel secure, not wobbly, and won’t come out once you turn the table over.  Keep the bolts center and straight in the legs. If they are misaligned, the legs will appear crooked when you attach them to the T-nuts. To make this part easier, put a pair of metal nots on the end of each hanger screw. Tighten them, slip the screw into the wood, and then use the nuts to tighten the screws. Finish by removing the nuts. The hanger bolts fit inside the threaded openings in the center of the T-nuts. Turn them clockwise as far as you can. Make sure the legs fit well against the table. Flip the table over when you’re done to see if the finished product looks level and sturdy. Keep twisting the legs until they are even with the table. The hanger bolts fit in the threaded holes in each T-nut, leading to a simple but effective installation that hides the hardware.
Purchase 4 T-nuts and hanger bolts. Position the T-nuts near the table’s corners. Drill 4 holes through the base of the tabletop. Tap the T-nuts into the holes with a hammer. Drill a pilot hole through the center of each table leg unless they have pre-installed hanger bolts. Screw the hanger bolts into the table legs. Twist the legs onto the T-nuts until they are even with the table.