Considering he is four years old, my son does a great job keeping his various Lego kits sorted and put away. He has figured out if any of those pieces get lost he will not be able to complete his model the next time around. Unfortunately, he has had no luck hanging onto the the instructions and catalogs that come with each kit. They get torn, ripped and bit by bit they find their way to the trash can or the vacuum bag.
His pile of instruction sheets have all but vanished. With a little hunting (actually, it wasn’t that hard) I was able to find a couple fantastic sites that have a comprehensive catalog of free viewable/printable Lego instructions and catalogs, some reaching as far back as 1958! So whether you are searching in vain for the instructions for that Lego 2005 Mini Dumptruck or an obscure set from the 70’s, there’s a chance you will find it in one of these databases (listed below).