A T-Nut is used to attach a bolt into wood or plastic instead of a wood screw. T-Nuts have a long, internally threaded barrel to thread bolt, a large flange with prongs to penetrate and secure nut in. T-Nuts generally come in 3-prong, 4-prong or 6-prong styles. The general rule of thumb is that the more prongs, the softer the material to fasten into (ie 3-prong for hard wood, 6-prong for softer plastic). T-Nuts are often used to attach table legs with the use of a Hanger Bolt.