Rebars are fundamental for the building carcass, they can not be used as a cover due to their structure. Some of the bars are made of molded steel couplers that strengthen the bars itselves. Rebar coupling systems http://www.hardman-de.com/technology/rebar-coupling-equipment.html used by companies including Hardman-de provide really sustainable constructions. Hardman’s steel cylindrical couplers have a “jumper” inside at the center so that the two pieces of rebar are centred perfectly and easily. A full-strength joint increases elongation of the coupler to 7—10%.