Blade-Tech Industries builds the belt hardware that most of the Kydex world is already drilled for. Their Tek-Lok and Molle-Lok attachments are the standard aftermarket upgrade when a sheath ships with a loop you cannot stand, a clip that rides at the wrong angle, or no belt option at all. If you have bought a fixed blade in the last decade, there is a good chance the sheath already has the hole pattern for one of these.
The Tek-Lok is the one people mean when they say they are swapping the hardware. It is a hinged two piece frame that clamps around the belt instead of threading onto it, which means you can move a sheath from a work belt to a hunting belt without unbuckling anything. Two adjustable shims size the channel to your belt, anywhere from a 1.5 inch EDC belt up to a 2.25 inch duty belt. A rotating secondary lock sits over the primary release so the thing does not pop off when you drag a hip across a truck seat. Nine mounting holes on a three quarter inch grid let you run the sheath vertical, horizontal, or canted forward or back. Molded in the USA from glass filled nylon, and originally patented by Tim Wegner and Robert Terzuola.
The Molle-Lok solves the other half of the problem. It weaves through standard PALS channels on a plate carrier, chest rig, pack, or duty belt and locks down with a spring loaded stainless pin, so the sheath stays put under movement instead of walking around the webbing. Six holes on each side give you height options, and both the small and large versions run the same three quarter inch hole spacing as the rest of the Blade-Tech system. The small Molle-Lok is the common pairing for molded ESEE sheaths carried directly on load bearing gear.
Most aftermarket Kydex is cut to the Blade-Tech pattern, so this hardware drops straight onto sheaths from makers like Bradford and custom work from Yellow Hawk. Screws, posts, and spacers come in the kit. The IWB belt loops here cover the other direction, dropping a sheath inside the waistband where a Tek-Lok would print.