Carpet on carpet

Metheven

We put a length of hard backed carpet runner on top of the caravan carpet near the door, but whatever I try I cannot stop the top one 'creeping' along the underneath one, just a few steps on it will shift it a few inches.

I've tried the plastic pointed carpet backings that stick to the underneath of the top carpet and supposedly bite into the one beneath but makes no difference. Other than nailing it down  have you found a way to stop one from 'walking' on the other.