On 2010-11-21, Michael A. Terrell wrote:
A hollow oval head used for CATV equipment. Hamlin used them on
their descramblers. You could get them out with a pair of dykes, but
nor without destroying the screw and damaging the case. Either cost the
customer their account, and they could never get cable service with our
company, anywhere in the US. A list of violators was kept, along with
their personal information for future reference.


Sounds like a pretty smart solution to customer malfeasance.