The Basics: Folding Knife locks
Bleh. This is the type of lock you can find in your run of the mill Swiss Army knife. If you aren’t going to be doing anything too serious or that requires a lot of force, this style of lock is fine. Anything more, though, and you will definitely want a real lock.
An oldie but a goodie. The lockback is one of the oldest locking mechanisms, and was really popularized by the Buck 110, one of the most famous folding knives ever. Lockbacks offer premium security, with a mechanism that won’t wear down with repeated use. One major downside is how difficult it is to close a lockback knife one handed- with certain knives, like much of Spyderco’s line, this is easier but still dangerous.
Another very popular style, the liner lock relies on a scale of metal between the handle scales to keep the knife locked open. For one handed open and closing it doesn’t get much easier than this. One major downside is that liner-locks do tend to fail more often than framelocks or lockbacks, and repeated use can wear down the metal scale of the lock, eventually rendering it useless. At that point, unless you purchased from a company that guarantees your knife for life, you’re pretty much screwed.
This is a beefier version of the liner-lock, with the locking scale integrated into the frame of the handle itself. The most famous, and best, example of this is the Sebenza by Chris Reeve (which is also one of the best production folders on the planet). A framelock will generally be tougher than a liner, and easier to open and close then a lockback, but the usual caveat of repeated use wearing down the locking mechanism still applies here (although it would take significantly longer than a liner lock).
Axis LockBenchmade pioneered this style of lock, which uses a spring-mounted bar to hold the knife in place. Having handled quite a few of these over the years, this is by far the easiest locking mechanism to engage and disengage, one-handed or two handed. It is also very strong- I haven’t heard many accounts of the lock itself failing, except where there were some issues with the metal itself. There are two drawbacks to this style, however- first, the spring used to hold the bar in place gets loose over time, which makes the lock easier to (accidentally) disengage. Second, if you are using the knife in extremely tight spaces, the locking mechanism can get snagged and cause the blade to accidentally close.