The rectangular construction rule is used to control deviations from the straightness and parallelism of construction and other products, including the use of support prisms, as well as excellent for plastering and screeding, since the presence of 4 edges with a 90 ° angle increases the service life. Rectangular rules with a bubble level are used to form even layers of bulk materials, for example – to level the layer of expanded clay, when laying the elements of the prefabricated floor. They are also used to check the geometry of plastered surfaces and to create significant tile facings (to control the horizontal of laying).