The idea of a fixed piggyback boils down to one simple constant; the two sheaths are connected permanently. You can, if course, separate them by removing the hardware that connects them, but this requires tools and time to accomplish.
This is s concept I have been developing for a couple of years. The idea is that you have multiple knives (usually 2) on one larger system. You can use the setup the same as you would a fixed piggyback system. But when you need to, you’ll be able to separate the sheaths without the use of any tools. The smaller sheath will already be installed with its own carry setup, so you can immediately transition the smaller knife to a designated secondary carry position.
The TMMS is a modular mounting system designed and produced by the same company that manufactures the Tek-Lok. It is designed to work with a Tek-Lok. In so many words, this is a direct alternative to my UTA. There are some subtle differences, however. The TMMS is much like a side release buckle; one “male” prong, one “female” receiver. The prong is directly attached to the smaller sheath, while the receiver is attached to the larger sheath. You simply clip the prong into the receiver and they lock up and are joined to create a piggyback system. You can very quickly and easily separate them once more by squeezing the wings of the prong and lifting it out of the receiver. The TMMS comes with a second receiver, which attaches to a Tek-Lok. The Tek-Lok may remain on your belt at all times. When you want to, you can switch between the piggyback setup or belt carry. It is fast, easy, and secure. The biggest difference between the two Tek-Lok adapters is that your smaller sheath will be lower profile while attached to the piggyback with the TMMS, but slightly bulkier while on your belt. It will be bulkier while attached to the piggyback with my UTA, but slightly lower profile while on the belt. The cost of the TMMS will typically be lower as well, because it is a part I can order and install, rather than handcrafting it myself as I do with the UTA.
To piggyback a smaller sheath with an ulticlip onto a larger sheath, I create a shell that the smaller sheath can clip into. This is more or less a sheath for your sheath. The shell remains fixed to the larger sheath, allowing you to add or remove your smaller sheath at will, without the use of any tools, and immediately transition to wearing it with the ulticlip.
To piggyback a smaller sheath with an nylon dangler onto a larger sheath, I create a shell that the smaller sheath can clip into. This is more or less a sheath for your sheath. The shell remains fixed to the larger sheath, allowing you to add or remove your smaller sheath at will, without the use of any tools, and immediately transition to wearing it with the nylon dangler. While attached to the larger sheath, the dangler loop can be conveniently tucked behind the shell.