i dont know about getting my first knife, but my dad, being a scout leader, brought me up right with all those kind of things so i was using saws and axes very young as well as knives and was taught all about there safety. i became a bit of a pyromaniac which was good because i also knew all the fire safety stuff and had a lot of experience what to do when you get burned and what not to put on a fire! i was a very outdoorsy kid and never learned to ride a bike because i always fell off, gave up and went to find something in a bush somewhere. my dad saw that i never was going to so taught me to drive his Land Rover Defender 90 off-road at the age of 7 lol! i have a large collection of knives and other tools or as my friends would call "weapons" (they all think i'm an axe murderer). so i was trusted by my dad and bought up right and used all this stuff from a young age, probably as young as 3 or 4, so if you can trust your 4 year old then let him use a couple of your knives and then go to an outdoors shop and let him have a look at a few locking folders and let him pick a reasonably priced one. oh and stainless steel or you will be cleaning it or it will rust away.