I came up with this trick when I had to make use of RCA extensions to run my 8.1 surround sound in my office. I will not get into if you should or should not run extensions on a system because of signal degradation. All I know is that it works fine in my office.
Step 1: Connect Your Cables
Twist the cables like so and then pull them down tight like in the photo.
Step 2: Lock With a Zip Tie
Now I lock the whole thing with a zip tie right in the middle and nip off the extra tie. Finish this by trimming off the tiny amount of tie left sticking out of the lock with an Exacto knife. If you are intending to pull this through any spot put electrical tape on the leading end so it slips through the openings. I have only used this in false ceilings, but I can attest that this is a very durable connection. Unless you really abuse it it will remain connected.
Naturally this does not work on cables with spring style stress reliefs.