A non-contact voltage tester has a battery ... to trace the routes of various wires with the power on. A continuity tester ...

Enough is never enough. Although [David Johnson-Davies] has a couple of multimeters lying around, he still felt the urge to build a stand-alone continuity tester and has posted details for a super ...

No multi-meter? For troubleshooting most household things, a continuity tester is extremely handy. And as it turns out, you can make your own from the dollar store for next to nothing.