Braces, or suspenders, are an alternative to the traditional belt. Braces hold the trousers up by the shoulders. Traditionally, braces are worn without a belt and only on trousers that do not have belt loops. There are very strict rules about the correct placement of brace buttons, but the rules are not complicated. Use a pair of trousers that are slightly looser than trousers you would wear with a belt for the most authentic appearance to your braces.
Mark the placement of the brace buttons on the front side of the trousers. Place two pins jut over the front pleat about 2 inches down from the top of the trousers. Place two pins about 2 inches in from of the side seams on either side of the trousers.
Pin two pins in the back of the trousers to mark the placement of the back buttons. How to attach the back buttons will be determined by the style of braces. For "Y" shaped backs, place a button 2 inches on either side of the seat seam. For "X" style backs, place two buttons 4 inches apart from the back seat seam.
Thread the needle with two lengths of thread and tie a knot in the bottom of the thread. Sew the buttons to the marked areas with the concave side facing away from the trousers. Use parallel lines, or an "X" pattern when sewing the buttons in place. Sew through several layers of fabric in the waistband. You can sew all the way through the trousers as well, if desired. This looks better if you place the buttons on the outside. You can place the buttons inside or outside the waistband, depending on preference. Thread about five lengths of thread through each hole, then tie a knot in the end of the thread to secure.