cat5 cable joining

I had the occasion to have to add 12 feet of cat 5 cable
from my router to another computer.I bought an 8 wire
extension plug and put both cables together.But the
system did not work .I am told there is a twist in the
connectors and putting two together like that won't
work.Is the best way to do this now is to cut off the
ends of the cables and splice them together without using
the adapter plug.
Help if you can I am tripping over the wire on the floor.
Thank you ,
Ray Ingram