Electric installation - find connected corrugated pipes
The basic tool for installing wiring in conduit is a fish tape



It's nothing more than a stiff strand of steel, plastic, or fiberglass made to push into conduits.  You push it through the conduit, tie your wires to the end of it, and pull it back through.  

When you're not sure where the conduit goes, you will want a non-conductive fish tape - you don't know if it might come in contact with live wire, in an electrical panel, etc.