When I was a kid I "spliced" a line (connected it to screw terminals in the box on the side of the house) from my parent's main phone to the basement so I could

When I was a kid I "spliced" a line (connected it to screw terminals in the box on the side of the house) from my parent's main phone to the basement so I could shotgun two dial-up modems in the middle of the night (the basement already was wired for the 2nd fax/internet line). I wasn't explicitly trying to keep it a secret, but I also didn't tell anyone, my dad found it after a couple months when he tried to make a particularly late phone call and heard modem noise.