In article ,
"Jeff" writes:

What were those plastic cap type thingys that you screw on the cables to
join them, they were all over a factory where I used to work

"Screwits" is one brand name. A nicname they had back in the
days they were used was "dog ********" due to the way a pair
of them would hang down below a cable. They are still allowed
and commonly used in the US, who call them wire nuts, and are
a significant source of building fires.

Note that there are crimps which look similar too.

--
Andrew Gabriel