A carpet tack strip is a thin strip of wood studded with sharp nails or tacks.
It is used to hold carpet in place along edges. Carpet tack strips are typically installed by nailing them to the floor/landing. The carpet is then stretched over the tack strip and held in place by the pins.
In most cases a stair runner installed using a continuous length of material does not require a tack strip – however, it is needed when there is a break in the material. This is most often where a landing meets an upper section of stairs.