Just buy a challenge lock. You can set it yourself with all kinds of pin setups. Depending on the one you buy, you can set up a 3-pin with easy pins and go all the way to 5-pin or 7-pin with myriad security pins. The lock comes with a bag of pins and you can get another giant bag of security pins for another $10. That way you can put in a single security pin and see exactly how that works by itself. Then add more. Altogether it's actually cheaper than this, even with the extra bag of security pins.
Once you learn the idiosyncracies of each of these locks, you will learn nothing more from them ever again. You'll pick them automatically without thinking. A challenge lock lets you continually challenge yourself (thus the name). You also get a sense for how locks work, since you have to set it up yourself.
Once you learn the idiosyncracies of each of these locks, you will learn nothing more from them ever again. You'll pick them automatically without thinking. A challenge lock lets you continually challenge yourself (thus the name). You also get a sense for how locks work, since you have to set it up yourself.