Making plumb and level post, beams, supports, floors, tables, etc. is a very important part of fine craftsmanship and the safety of a structure. The imperative element of a builder's level is a sealed vial filled with a liquid containing an air bubble. Due to the slight curve of the glass, when the vial is held perfectly level the bubble will float to the middle. Electronic levels have moved this age old tool into the 21st century displaying the read out on an easy to read digital screen.