A belt buckle must be sized so the internal bar width matches the strap width exactly — 32mm buckle for a 32mm strap, and so on. The two main styles are heel bar (the most common for personal belts) and centre bar. Metal quality matters: a properly made buckle should feel substantial with no flex in the frame and a tongue that moves smoothly. Match the metal finish to any other hardware on the piece.
Making a leather belt requires firm vegetable-tanned leather at 3–4mm, a buckle matched to the strap width, and core skills: cutting, edge finishing, hole punching, and stitching. The key sequence is cut the strap, pre-finish the long edges before assembly, cut the buckle tongue slot, attach and stitch the buckle fold, punch the adjustment holes at even spacing, and add a keeper loop. Finishing the edges before the buckle is attached saves significant time and effort.