re: Sprinkler valve location?

Ok …I find this topic interesting.. I have chased sprinkler value boxes in my yard for thirty years.. to op that said how can you not find them.. well buy a house fifteen years old and have the original blueprints of the installation.. then find the modified location of when they actually install them.. and once found remark your blueprints or be lazy and do not and let grass grow over the box again..live in that house for thirty plus years as a do it yourself kinda of guy.

With that said I have them all marked but sometimes still have to poke around the grass.. gravel etc..

I googled wire tracer ..not sure I found the right thing.. how does this tool work.. tbh.. I am old and lazy and now pretty much just call my sprinkler guy.. but still interested and y’all’s method.. this would have helped a lot as I changed out valves when I was younger.