As a senior knife instructor for military and law enforcement — as well as a combatives practitioner for more than 37 years — I think the idea of having a usable backup edged weapon is vital. What I mean by usable is often we get very comfortable with having a folder on our person but don’t realize that getting that folder into play is a lot harder than one might think.
Try this exercise: Put your folder in your standard carry location. Do five circular pivots with one hand on a basketball or object on the ground then do to fine up/downs and deploy your edged weapon. Do this exercise 10 times. If you can get your blade into play 8 out 10 times quickly then you have a solid base line to work from. If you find yourself fumbling with your blade and have to do two-handed openings you should either:
A) Learn a new deployment technique
B) Buy a new folder that you can deploy quickly without fail
C) Get a fixed blade that you can get a positive grip on in wet, dark, and in a startled state