Individual reinforcing bars are joined together to form the reinforcement cage, generally using tying wire. The connections should be sufficiently rigid so that the bars do not move during the concreting process.
It is generally not necessary to tie every bar intersection but the ends of bars should be tied. In beams and columns it is normal to tie every intersection of links to corner bars but only at alternate intersections of other main bars. In some cases, particularly for precast concrete units, tack welding is used though this can affect the properties of the steel locally.
The reinforcement should be clean to ensure that there is adequate bond with the concrete. Any loose rust on the surface will generally be removed during handling and fixing the bars; a light layer of rust that is firmly adhered to the bars will not affect the bond and is not detrimental.