At the other is a rectangular device with prongs or teeth that sink through the pile into the carpet backing. The rectangular head stretches the carpet by applying leverage. A knee-kicker is only about 2 feet in length. The carpet is stretched as the layer pounds his knee against the cushion. The rigidity of carpet back makes it virtually impossible to be stretch properly with a knee-kicker in a standard size room.
Tension is all that holds carpeting on the tack strip.
The use of a power stretcher is mandatory to achieve proper tension. But, many carpet layers will use the knee-kicker only, whatever the size of the room, because the work go faster. However, the carpeting, for lack of proper tension, will come loose from the tack strip, and, in time, rippling is probable, which can lead to carpet backing separation. The moment the carpet layer arrives to install your carpeting, you should make it quite clean that he must use a power stretch in every room possible. Seam sealer should be used on all carpet seams.