I use insulbright when I want them to double as long hot pads for serving dishes. When I'm out of insulbright I use pre-shrunk warm and natural. Both quilt up flat. I always iron when complete and after each washing.

Pellon fleece interfacing - it's sold both fusible and non fusible. It gives the runner body without the concern of a candle being unstable. I've never used anything else and I don't think I will.

I do this too with my table runners, my sister loves it cause she doesnt have to remove it from the table to serve dinner, just put the pots right on. I will say she doesnt keep anything on the runner, so I actually added batting and insul-bright, SID, and viola!

I use preshrunk flannel in mine. I want them to be used when I set the table for a dinner as they match the placemats. However, I set the hot dishes on wooden trivets so the runners do not have to protect the table. They do have to lay absolutely flat on the table.

My guild sisters go with regular or light batting, sometimes with flannel. My preference is generally regular batting.

Wow, look at the varied answers!!! I use craft felt that I buy by the yard. It is available in different widths and I try to get the widest.

piney

I use fusible fleece, and they turn out beautiful..... no basting or pinning either!

I like Hobbs Theremore batting. It's very thin but a bit firm. Quilts easily. Tablerunners have some definition but lie flat. I use a coupon at Hobby Lobby to get mine. One package does a lot of tablerunners.

I use flannel,preshunk and it works ok.

A layer of osnaburg, muslin in bleached calico would make thin flat runners with a good stabiliser in centre, especially if you have a different colour runner each side,