ADAM HART-DAVIS / SCIENCE PHOTO LIBRARY ADAM HART-DAVIS / SCIENCE PHOTO LIBRARY
Spirit level. Close-up of a spirit level used to measure how horizontal a surface is. It consists of a tube filled with fluid except for a single bubble. When the spirit level is placed on a horizontal surface, the bubble remains between the two vertical lines in the clear part of the tube (as here). However, the bubble will move along the tube and beyond the markings if the surface is not horizontal.
Model release not required. Property release not required.