 While most cats seem to prefer tall cat trees, some prefer options which offer shelter or a secluded escape, which may be at any height of the structure.Conventional cat tree designs are of a floor based solid structure, composed of square shaped sheets of particle board (as platforms, boxes and enclosed structures) combined with wooden studs and planks (used as elevators and/or stairs), with exteriors and interiors typically covered with carpet.Elevators are also frequently covered with an abrasive materials (sisal rope being the most common), intended to inducing cats to scratch in those areas and reduce overall wear of the structure.