knives were most commonly built as linerlocks. Blade lengths varied from , but the most typical models never exceeded in blade length for legal reasons in most US jurisdictions. In response to the demand for these knives, production companies offered mass-produced tactical folding knives. Companies such as Benchmade, Kershaw Knives, Buck Knives, Gerber, CRKT, Spyderco and Cold Steel collaborated with tactical knifemakers; in some cases retaining them as full-time designers. Tactical knifemakers such as Ernest Emerson and Chris Reeve went so far as to open their own mass-production factories. Presenting any folding knife as a weapon, rather than a utility tool, has met criticism. Many who’ve studied knife fighting point out that even the strongest locking mechanisms have some risk of failure, so a folding knife is never going to be as reliable as a fixed-blade combat knife. Lynn Thompson, martial artist and CEO of Cold Steel, noted in an article in Black Belt magazine that most tactical folding knives are too short to be of much use in a knife fight. And while his company does make and sell a tactical folder, it is not the best option during an actual fight. The case for tactical folding knives, then, is that a less-than-ideal knife in your pocket is always more useful than an ideal knife left at home. A 10-inch fixed-blade Bowie knife, for example, may be far better for combat, but it is far less practical — and often illegal — to carry around in day-to-day life. And should there be a need to take defensive action, there’s rarely enough forewarning to plan ahead which knife to carry that day. Other features Traditional folding knives are opened using nail-nicks, or slots where the user's fingernail would enter to pull the blade out of the handle. This became somewhat cumbersome and required use of two hands, so there were innovations to remedy that. The thumb-stud, a small stud on the blade that allows for one-handed opening, led the way for more innovations. One of these is the thumb hole: a Spyderco patent where the user presses the pad of the thumb against a hole and opens the blade by rotating the thumb similarly to using the thumb-stud. Another innovation of Sal Glesser, Spyderco founder, was the clip system, which he named a "Clip-it". Clips are usually metal or plastic and similar to the clips found on pens except thicker.