Srinkage joints are obligatory every 25 m² in a concrete slab; They are used to control cracking. Usually they are made by a saw cut, our product is an alternative of the saw cut which don't let a quality finish and oblige to come back to the site when concrete is dry. The joint rule for concerte slabs is a hollow PVC profile to make shrinkage and crack control joint. It is set the day before pouring on small concrete heaps. Profiles are set to the finish level of the slab. Afterwards you pour the concrete and you lay it to the correct level with the joint rules used as a sliding guide. When thez concrete is layed job is finished you don't have to come back to make usuals saw cuts ...