A door is distinguished by recessed panels enclosed by stiles, rails, and muntins. The parts of the frame are joined together with wooden pegs or nails. To make the process of building doors more efficient, some manufacturers combine different components such as stiles, rails, and muntins at one time. This reduces the amount of wood that must be cut to build a door. During the colonial period, most doors were made from wood. Before metal became available, people turned to wood for their doorways because it was easy to work with and provided many opportunities for design. Even after metal came into use, most doors were still made from wood because they offered better security than their metal counterparts. By the late 18th century, iron was commonly used instead of wood for doors that were not expected to face extreme weather conditions. As time went on, engineers began to develop new inventions that could be used in buildings. One such invention was the door lock. The first locks were made from brass and included keyholes. They were attached to the inside of doors so people could lock them from the outside. Later designs included knobs or handles you could turn to unlock the door. These locks prevented people from entering your home without your permission.