Menus are sometimes hierarchically organized, allowing navigation through different levels of the menu structure. Selecting a menu entry with an arrow will expand it, showing a second menu (the sub-menu) with options related to the selected entry.
Torsion springs are normally mounted horizontally above the opening of your garage door. When you pull the door down, cables attached to the bottom corners actually force the springs to wind up, in turn energizing the system.
Spring Loaded Hinges. One specific model of self closing door hinges, uses the friction caused by opening the door to pull a spring. This spring uncoils as the door is opened, and when you let go, the spring closes the door by pulling back to its natural state.