In babyproofing our home, we purchased several drawer and cabinet locks. They are a relatively inexpensive way to keep your little children out of cabinets containing things they should not play with.
These locks consist of a small piece of plastic that is spring-loaded. You mount the piece on the back side of a cabinet or drawer and the piece will hook onto the underside of the facing of the cabinet, locking it into place. To open the cabinet, simply open the door slightly and depress the plastic piece and it will release it.
These cabinet and door locks work pretty well. Neither of my children have ever been able to manipulate the lock to open it themselves. The problem we have run into is that if they open and close it enough (unsuccessfully), the plastic piece can become damaged (or the wood that it latches onto) and it will wear out. I've had to remove these from three of the five cabinets we've locked using them.
These are a little difficult to install, as you have to screw the plastic piece into place. Now that we've removed a few of these, there are now holes in the doors of our cabinets where the locks used to be.
Overall, I would not highly recommend these locks. They may work well in an area where your children do not spend a lot of time (perhaps in a workshop or garage), but in an area such as a kitchen where children are constantly trying to open things, these locks just aren't durable enough.