cross-laminated timber (CLT), manufactured wood panels that consist of layers of boards glued together under pressure with the grain of the boards in one layer running perpendicular to the grain in adjoining layers. Panels produced for use in interior and exterior walls typically have three or five layers while those for floors and ceilings have three to 7 layers. The lengths of the prefabricated panels may be up to 52 ft (16 m), and they can be produced with door and window openings and service channels largely precut. As a result, the panels may be relatively quickly assembled on site, allowing for shorter building construction times. The panels are stronger than traditional wood frame construction, and are resistant to fire, which will tend to char the panels but not burn through. Interlocking CLT, which instead of adhesive uses tongue-and-groove joints to link a layer's boards and dovetail joints to bond the layers, is under development. CLT was first used in Switzerland and Austria in the 1990s and since has been widely used in Europe for residential, commercial, and institutional construction, ranging from low-rise to mid-rise buildings. It was first used in North America in 2010.