Hidden Defense: Hip Grip/Mexican Carry Trigger Holster
Can't do justice to the whole page by copying, hit the link then go to the bottom for video and pics...
Relevant section:
I'd read about a knife holster several weeks back when I was researching neck knives. The holster could also be used with the knife in the pocket. When the knife is put into play and pulled out of the pocket a chain or cord tied to the holster and attached to a belt loop would catch the holster and uncover the knife blade so that it can do it's work while safely clearing the pocket. Why can't a similar "trigger holster" be made for those of us who decide to mexican carry. Here's what I've come up with: