I'm not sure I want to ask this, but what will the result be of sticking a pin in the cable line?
I thought I remembered hearing years ago that it would ruin the whole system. Could be wrong.
The short circuiting of the center conductor to the shield which is ground. No reception and possibly damaged equipment.
On the coax cable of a transmitting device like a Ham radio, this can EASILY destroy the amplification circuits of your amp or radio...or both.
That's why all cable below 20 feet is armored and hidden on all my rigs.
Your cable TV line is 'co-axial', meaning there is an outer mesh shield (ground) and a center conductor (signal). A needle will effectively short the signal out, then take a wire cutter and cut the needle flush with the outter plastic - he won't have cable/internet and until he finds or replace the cable.