Vertical Angles

This is a pivot leg attached to a tray table. It contains two pairs of vertical angles (one has been outlined in red, and the other in green). It forms these angles since the angle at which the table opens is the same as the angle at which the legs open because vertical angles are congruent. Pivot legs can be found on objects of expandable furniture such a tables and chairs. It makes these tables and chairs easier to fold and store. I found this pivot leg on a tray table in my house's basement. Directors and actors have been known to stereotypically sit in chairs with pivot legs. These legs are frequently used for big events such as weddings or parties as they can be easily set up then taken down.