Mats or rugs can be torn by handling or excessive wear. The resulting loose or raised areas can catch footwear, creating tripping hazards . Mat or rugs that have been moved and not properly re-laid may develop curled or raised edges, which also create tripping hazards. Mats or rugs that are not laid flat or fastened securely may pucker, causing toes or heels to catch, leading to falls. Grease or water can make mat or rug surfaces slippery. Also, when mats or rugs are not suited to the surfaces they cover or are laid with the wrong side down, they may slip, creating greater hazards than the surfaces they cover.