So sorry to hear that your runner mat is slipping on your hall carpet. I can confirm that you do have the correct backing (Multi Grip) to go on to carpet, but Turtle Mat doesn’t advertise non-slip, only anti-slip to minimise creep, as there are so many different floor finishes to take in to consideration. However, one possible reason for your mat slipping could be that the nap of the carpet is laying in the same direction, when you place you mat on top the pile may also be laying in the same direction. If so this may explain the movement that you are experiencing. Also the backings can be a bit shiny from the manufacture which varies from batch to batch, and a few machine washes normally resolves this. I do hope this is a help.
Rebecca Wilson