Torsion springs and extension springs are the two most lifting components which aid in holding the weight of the garage door as the motor lifts/lowers the door (or as a person manually lifts/lowers the door, for manual-operation garage doors). Extension springs are the most common spring in household doors, and they are heavy-duty springs that extend as the door is lowered, reducing the effort necessary to move the weight of the door. Similarly, torsion springs reduce the effort to move a garage door, but these springs are coiled in design, and they create torque instead of lift, moving a garage door at an angle, instead of in a straight line. Torsion springs are far less common today, especially in residential applications, since they must be customized depending on the weight of the door, and because they are more expensive. However, torsion springs are generally safer, and they may be the best choice for heavier doors.