For a liner lock, as already said, there is a detent micro sphere pressed into the spring/liner at te upper corner usually that "falls" into a little blind hole drilled in the flat face of the blade in closed position. It looks not enough but if done properly it can stop the blade from opening quite well and safely. For the lock back: in closed position it works exactly like a slipjoint, with the head of the spring pressing down the heel of the blade beyond the pivot so that the blade rises inside the handle. Although, I designed, some months ago, a lock in closed position that works perfectly, but it is not simple because you have to do it very last thing on the knife, so if you give just a single file stroke too much you can jeopardize the whole thing.
I attached a couple of pics. This is the way I use, I like to reduce the quantity of pieces in my knives. The spring is one piece with the back. In those pics it is oversized, I carefully grind it after HT to reach the strength I desire. This way of making the mechanism allows me to reduce a little the size of the butt of the handle. I put just one pin at the end of the spring to force it upwards. This spring is MA5M (420C) but you can make it in any carbon steel you want. I'd rather use C45 (1045 I think) because it decreases the possibilities of breaking since I usually close my folders with rivets and not with screws.
This is just my experience I hope it helps
Francesco