Flat Head/Martini Bolts are mostly used with small feet and shallow bolt depths. Button head molds are mostly used on DIY wood holds. All bolts are manufactured with a unique Cold-Forging technique that results in greater strength, higher fatigue resistance, and threads that last! Using high quality bolts is critical if you want to get the longest life possible out of your t-nuts. Use Alloy Steel bolts indoors, and Stainless Steel if you’re outside in a high humidity area. These are not fully threaded bolts.