I had a little time this weekend and came up with an improved dangler design. Of course, "improved" isn't all that hard given my previous design consisted of a piece of cord, tied in a knot
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I started with an old piece of webbing with a tri-glide on it and a quick-link (both things I had floating around that I kept because they might come in handy some day).
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I cut the webbing down to about 11 inches and made it into a loop; I doubled over the end that I fed through the tri-glide and sewed it so it so the webbing end cannot fit back through the tri-glide. Then I put the quick-link on the sheath's belt loop.
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Finally, by putting the small webbing loop I made through the quick-link as well, I had an adjustable dangler that seems like it will do the job well:
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This not only seems more secure than my previous set-up, but it is easily adjustable depending on how much "dangle" I want.