Over time, your carpet can loosen up and develop ripples. In most cases, this is because the original installer only used a carpet knee-kicker to install the carpet rather than a carpet power-stretcher. But a knee-kicker was never designed or intended to be used to stretch carpet. It is only to be used to aid in the stretching process. It just doesn't adequately stretch without the use of a power-stretcher. A power-stretcher has a large power head and uses a series of extension poles to span the length of the entire room. It braces against one wall and power-stretches the carpet to the opposite wall until the whole room is back under the proper tension, as intended by the carpet manufacturer. It's critical to have your loose carpet stretched as soon as you notice ripples in order to avoid delamination of the carpet backing or other permanent damage due to the raised ripples. The raised ripples can also pose a major trip hazard, particularly for small children and the elderly.